Multi-layer core golf ball

ABSTRACT

A golf ball comprising a core and a cover, wherein the core consists of: a solid inner core layer formed from a transparent or plasticized polyamide composition and having a diameter of 1.10 inch or less and a center Shore C hardness (H center ) of 50 or less, one or more optional intermediate core layers, and an outer core layer formed from at least one of a thermoset rubber composition and a thermoplastic composition and having a thickness of 0.200 inches or greater and an outer surface Shore C hardness (H outer surface ) of 70 or greater, wherein H outer surface  &gt;H center , and H outer surface −H center ≧40. In another embodiment, the center Shore C hardness (H center ) is 40 or less, the outer surface Shore C hardness (H outer surface ) is 85 or greater, and H outer surface −H center ≧45. In one embodiment, an intermediate layer is disposed between the outer core layer and the cover.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation-in-part of the following:co-pending U.S. patent application Ser. No. 14/248,618, filed Apr. 9,2014 (the '618 application”); co-pending U.S. patent application Ser.No. 14/248,487, filed Apr. 09, 2014 (the '487 application”); co-pendingU.S. patent application Ser. No. 14/527,835, filed Oct. 30, 2014 (“the'835 Appln.; and co-pending U.S. patent application Ser. No. 14/285,871, filed May 23, 2014 (“'871 Appin.”). The '618 Appin. is acontinuation-in-part of co-pending U.S. patent application Ser. No.14/248,487, filed Apr. 9, 2014, which is a continuation-in-part of bothco-pending U.S. patent application Ser. No. 13/958,854, filed Aug. 5,2013(“'854 Appln.”) and co-pending U.S. patent application Ser. No.14/035,074, filed Sep. 24, 2013. The '835 Appln. is acontinuation-in-part of the co-pending '618, '854 and '871 Applications.Meanwhile, the '871 Appin. is a continuation-in-part of co-pending U.S.patent application Ser. No. 13/451,671, filed Apr. 20, 2012. The entiredisclosures of each of these applications are hereby incorporated hereinby reference in their entireties.

FIELD OF THE INVENTION

The present invention relates to multi-layer golf balls having a veryhigh positive gradient core, including a very soft, low compressioninner core layer formed from an unfoamed composition.

BACKGROUND OF THE INVENTION

U.S. Pat. No. 8,182,368 to Kamino et al. discloses a golf ball whereinthe difference between the JIS-C hardness H4 of the core at its surfaceand the JIS-C hardness H3 of the core outer layer at its innermostportion is equal to or greater than 10.

U.S. Pat. No. 8,007,376 to Sullivan et al. discloses a golf ball havingan inner core layer with a negative hardness gradient and an outer corelayer with a positive hardness gradient.

U.S. Pat. No. 7,410,429 to Bulpett et al. discloses a golf ball whereinthe hardness of the inner core outer surface is the same as or lowerthan the hardness of the geometric center and the hardness of the outercore layer outer surface is greater than the hardness of the innersurface.

U.S. Pat. No. 6,695,718 to Nesbitt discloses a golf ball including acenter core component preferably formed from a sulfur-curedpolybutadiene and a core layer component preferably formed from aperoxide-cured polybutadiene and a metal salt of a fatty acid.

Despite these, and additional disclosures of golf balls having varioushardness gradient properties, there remains a need for a very highpositive gradient core, including a very soft, low compression innercore layer formed from an unfoamed composition. Such core would providegood durability while also contributing to spin reduction.

SUMMARY OF THE INVENTION

A golf ball of the invention produces a desired spin profile of reducedspin off the driver meanwhile maintaining moderate spin off wedges andirons.

Inner Core Layer Formed From a Transparent or Plasticized PolyamideComposition, Outer Core Layer Formed From at least one of a ThermosetRubber Composition and a Thermoplastic Composition

In one embodiment, the invention is directed to a golf ball comprising acore and a cover. The core consists of an inner core layer, one or moreoptional intermediate core layers, and an outer core layer. The innercore layer is formed from a transparent or plasticized polyamidecomposition P_(t/) _(p), and has a diameter of 1.10 inch or less and acenter Shore C hardness (H_(center)) of 50 or less. The outer core layeris formed from at least one of a thermoset rubber composition and athermoplastic composition, and has a thickness of 0.200 inches orgreater and an outer surface Shore C hardness (H_(outer surface)) of 70or greater. The outer surface hardness of the outer core layer is atleast 40 Shore C points greater than the center hardness of the innercore layer (that is, H_(outer surface)>H_(center), andH_(outer surface)−H_(center)≧40). In an alternative embodiment, thecenter Shore C hardness (H_(center)) is 40 or less, the outer surfaceShore C hardness (H_(outer surface)) is 85 or greater, and outer surfacehardness of the outer core layer is at least 45 Shore C points greaterthan the center hardness of the inner core layer (that is,H_(outer surface)>H_(center), and H_(outer surface)−H_(center)≧45).

The center Shore C hardness H_(center) is greater than 0 and up to 50.In one embodiment, H_(center) is from about 25 to 50.

The inner core layer may have a diameter of from about 0.10 inch to 1.10inches. For example, the inner core layer may have a diameter of fromabout 0.10 inch to 1.0 inch, or from about 0.25 inch to 0.90 inch, orfrom about 0.45 inch to 0.85 inch.

The inner core layer may have an inner core outer surface Shore Chardness (H_(icos)) that differs from the center Shore C hardnessH_(center) by up to about 5 Shore C. That is, in some embodiments,H_(center) is greater than H_(icos) by up to 5 Shore C, and in otherembodiments, H_(center) is less than H_(icos) by up to about 5 Shore C.In still other embodiments, H_(center) and H_(icos) are substantiallythe same.

In one embodiment, the outer surface Shore C hardness H_(outer surface)is from 70 to about 95. In another embodiment H_(outer surface) may begreater than 75 and less than about 85. In still other embodiments,H_(outer surface) may be from about 75 to about 95.

The outer core layer has an outer core interface Shore C hardness(H_(outer core interface)) as shown in FIG. 1 and described herin.

In one embodiment, the outer surface Shore C hardness H_(outer surface)is greater than an outer core layer interface Shore C hardness(H_(outer core interface)) by greater than 30. In another embodiment,the outer surface Shore C hardness H_(outer surface) is greater than theouter core layer interface Shore C hardness H_(outer core interface) byfrom 10 to 30. In yet another embodiment, the outer core layer interfaceShore C hardness H_(outer surface) is greater than the outer core layerinterface Shore C hardness H_(outer core interface) by less than 10.

The outer core layer has a thickness of at least 0.200 inch, and asgreat as about 0.780 inches, for example. In one embodiment, the outercore layer may have a thickness of greater than 0.250 inch and up toabout 0.450 inches. In still another embodiment, the outer core layermay have a thickness of greater than 0.200 inch and up to about 0.350inches.

In another embodiment, the outer surface Shore C hardnessH_(outer surface)−the center Shore C hardness H_(center)≧about 45. Inyet another embodiment, the outer surface Shore C hardnessH_(outer surface)−the center Shore C hardness H_(center)≧about 50. Instill another embodiment, the outer surface Shore C hardnessH_(outer surface)−the center Shore C hardness H_(center)≧about 55. In analternative embodiment, the outer surface Shore C hardnessH_(outer surface)−the center Shore C hardness H_(center)≧from 40 toabout 80. In one embodiment, the outer surface Shore C hardnessH_(outer surface)−the center Shore C hardness H_(center)≧from 40 toabout 70.

The inner core layer meanwhile has an inner core interface Shore Chardness (H_(inner core interface)). The inner core layer has a negativehardness gradient wherein the inner core interface Shore C hardness(H_(inner core interface)) is less than the center Shore C hardness, ora zero hardness gradient wherein the inner core interface Shore Chardness (H_(inner core interface)) is within 1 Shore C unit of thecenter Shore C hardness, or positive hardness gradient wherein innercore interface Shore C hardness (H_(inner core interface)) is greaterthan the center Shore C hardness.

The inner core layer may have an overall zero hardness gradient betweencenter Shore C hardness (H_(center)) and interface Shore C hardness(H_(inner core interface)), whereinH_(inner core interface)=(H_(center)). Or, in another embodiment,−1<H_(inner core interface)−H_(center)<1. In yet another embodiment, theinner core layer may have a positive hardness gradient between centerShore C hardness (H_(center)) and interface Shore C hardness(H_(inner core interface)) wherein:

1<H _(inner core interface) −H _(center)<45,

or 1<H _(inner core interface) −H _(center)<15,

or 1<H _(inner core interface) −H _(center)<5.

For example, in one embodiment, 1<H_(inner core interface)−H_(center)≦5.In another embodiment, 2<H_(inner core interface)−H_(center)≦5. In yetanother embodiment, 3<H_(inner core interface)−H_(center)≦5. In analternative embodiment, 4<H_(inner core interface)−H_(center)≦5.

In other embodiments, the inner core layer may have an overall negativehardness gradient. For example, in one embodiment,−1>H_(inner core interface)−H_(center)≧−5.

In one embodiment, the outer core layer has an outer core interfaceShore C hardness (H_(outer core interface)) such that the Shore CH_(outer core interface)−the Shore C H_(inner core interface)≦the ShoreC H_(outer surface)−the Shore C H_(center). This occurs, for example,where: (i) the Shore C H_(inner core interface)>the Shore C H_(center),and the Shore C H_(outer core interface)=the Shore C H_(outer surface);(ii) the Shore C H_(inner core interface)=the Shore C H_(center), andthe Shore C H_(outer core interface)<the Shore C H_(outer surface);(iii) the Shore C H_(inner core interface)>the Shore C_(center), and theShore C H_(outer core interface)<the Shore C H_(outer surface); and/or(iv) the Shore C H_(inner core interface)=the Shore C H_(center), andthe Shore C H_(outer core interface)=the Shore C H_(outer surface).

A non-limiting example of (i) is where the Shore CH_(outer core interface) (88)−the Shore C H_(inner core interface)(47)≦the Shore C H_(outer surface) (88)−the Shore C H_(center)(42). Inturn, an example of (ii) is where the Shore C H_(outer core interface)(83)−the Shore C H_(inner core interface) (42)≦the Shore CH_(outer surface) (88)−the Shore C H_(center)(42). And an example of(iii) is where the Shore C H_(outer core interface) (83)−the Shore CH_(inner core interface) (47)≦the Shore C H_(outer surface) (88)−theShore C H_(center)(42). Finally, one example of (iv) is where the ShoreC H_(outer core interface) (88)−the Shore C H_(inner core interface)(42)=the Shore C H_(outer surface)+(88)−the Shore C H_(center)(42).

In another embodiment, the outer core layer has an outer core interfaceShore C hardness (H_(outer core interface)) such that the Shore CH_(outer core interface)−the Shore C H_(inner core interface)>the ShoreC H_(outer urface)−the Shore C H_(center). This occurs, for example,where: (v) the Shore C H_(inner core interface)<the Shore C H_(center),and the Shore C H_(outer core interface)=the Shore C H_(outer surface);(vi) the Shore C H_(inner core interface)=the Shore C H_(center), andthe Shore C H_(outer core interface)>the Shore C H_(outer surface); or(vii) the Shore C H_(inner core interface)<the Shore C H_(center) andthe Shore C H_(outer core) interface>the Shore C H_(outer surface).

A non-limiting example of (v) is where the Shore CH_(outer core interface) (88)−the Shore C H_(inner core interface) (37Shore C)>the Shore C H_(outer surface) (88)−the Shore C H_(center)(42).In turn, an example of (vi) is where the Shore CH_(outer core interface) (93)−the Shore C H_(inner core interface)(42)>the Shore C H_(outer surface) (88)−the Shore C H_(center)(42). Andan example of (vii) is where the Shore C H_(outer core interface)(93)−the Shore C H_(inner core interface) (37)>the Shore CH_(outer surface) (88)−the Shore C H_(center)(42).

In one non-limiting embodiment, the transparent or plasticized polyamidecomposition comprises at least one of a polyether block amide, anamorphous polyamide and a microcrystalline polyamide.

Meanwhile, the outer core layer may comprise at least one of naturalrubber, polybutadiene, polyisoprene, ethylene propylene rubber (EPR),ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber, butylrubber, halobutyl rubber, polyurethane, polyurea, acrylonitrilebutadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinatedisoprene rubber, acrylonitrile chlorinated isoprene rubber,polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide,polysiloxane, polyester, alkyd, polyisocyanurate, polycyanurate,polyacrylate, and combinations thereof.

The outer core layer may alternatively or additionally comprise at leastone of ionomers; highly neutralized ionomers; non-ionomeric acidpolymers; polyurethanes, polyureas, and polyurethane-polyurea hybrids;polyester-based thermoplastic elastomers; polyamides, copolymers ofionomer and polyamide, polyamide-ethers, and polyamide-esters;ethylene-based homopolymers and copolymers; propylene-based homopolymersand copolymers; triblock copolymers based on styrene andethylene/butylene; derivatives thereof that are compatibilized with atleast one grafted or copolymerized functional group; and combinationsthereof. For example, in one embodiment, the ionomer may comprise ahighly neutralized ionomer.

The intermediate core layer may comprise at least one of ionomers;highly neutralized ionomers; non-ionomeric acid polymers; polyurethanes,polyureas, and polyurethane-polyurea hybrids; polyester-basedthermoplastic elastomers; polyamides, copolymers of ionomer andpolyamide, polyamide-ethers, and polyamide-esters; ethylene-basedhomopolymers and copolymers; propylene-based homopolymers andcopolymers; triblock copolymers based on styrene and ethylene/butylene;derivatives thereof that are compatibilized with at least one grafted orcopolymerized functional group; and combinations thereof. For example,in one embodiment, the ionomer may comprise a highly neutralizedionomer.

The intermediate core layer may alternatively or additionally compriseat least one of natural rubber, polybutadiene, polyisoprene, ethylenepropylene rubber (EPR), ethylene-propylene-diene rubber (EPDM),styrene-butadiene rubber, butyl rubber, halobutyl rubber, polyurethane,polyurea, acrylonitrile butadiene rubber, polychloroprene, alkylacrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinatedisoprene rubber, polyalkenamer, phenol formaldehyde, melamineformaldehyde, polyepoxide, polysiloxane, polyester, alkyd,polyisocyanurate, polycyanurate, polyacrylate, and combinations thereof.

In one embodiment, an intermediate layer may be disposed between theouter core layer and the cover.

Further and different constructions are as follows.

Outer Core Layer TP, Incorporating Transparent or Plasticized Polyamidesand Inner Core Layer formed from an unfoamed first thermoplasticcomposition TP₁

In a different construction, outer core layers may be formulated tocomprise a transparent or plasticized polyamide. For example, the golfball comprises a core and a cover, the core consisting of an inner corelayer, one or more optional intermediate core layers, and an outer corelayer. The inner core layer is a solid layer formed from an unfoamedfirst thermoplastic composition TP₁, and has a diameter of 1.10 inchesor less and a center Shore C hardness (H_(center)) of 50 or less. Theouter core layer is formed from a second thermoplastic composition TP₂comprising a transparent or plasticized polyamide, has a thickness of0.200 inches or greater, and an outer surface Shore D hardness(H_(outer surface)) of 55 or greater. Meanwhile, the Shore D hardness ofthe outer surface, plus 30, is greater than the center Shore C hardnessof the inner core layer by at least 40.

The center Shore C hardness H_(center) is greater than 0 and up to 50.In one embodiment, H_(center) is from about 25 to 50.

The inner core layer may have a diameter of from about 0.10 inch to 1.10inches. For example, the inner core layer may have a diameter of fromabout 0.10 inch to 1.0 inch, or from about 0.25 inch to 0.90 inch, orfrom about 0.45 inch to 0.85 inch. The inner core layer may have aninner core outer surface Shore C hardness (H_(icos)) that differs fromthe center Shore C hardness H_(center) by up to about 5 Shore C. Thatis, in some embodiments, H_(center) is greater than H_(icos) by up to 5Shore C, and in other embodiments, H_(center) is less than H_(icos) byup to about 5 Shore C. In still other embodiments, H_(center) andH_(icos) are substantially the same.

In one embodiment, the outer surface Shore D hardness H_(outer surface)is from 55 to about 95. In another embodiment H_(outer surface) may begreater than 65 and less than about 85. In still other embodiments,H_(outer surface) may be from about 75 to about 95.

In one embodiment, the outer surface Shore D hardness H_(outer surface)is greater than an outer core layer interface Shore D hardness(H_(outer core interface)) by greater than 20. In another embodiment,the outer surface Shore D hardness H_(outer surface) is greater than theouter core layer interface Shore D hardness H _(outer core interface) byfrom 10 to 20. In yet another embodiment, the outer core layer interfaceShore D hardness H_(outer surface) is greater than the outer core layerinterface Shore D hardness H outer core interface by less than 10.

The outer core layer has a thickness of at least 0.200 inch, and asgreat as about 0.500 inches, for example. In one embodiment, the outercore layer may have a thickness of greater than 0.250 inch and up toabout 0.450 inches. In still another embodiment, the outer core layermay have a thickness of greater than 0.200 inch and up to about 0.350inches.

In another embodiment, the outer surface Shore D hardnessH_(outer surface)+30—the center Shore C hardness H_(center)≧about 55. Inyet another embodiment, the outer surface Shore D hardnessH_(outer surface)+30—the center Shore C hardness H_(center)>about 70. Instill another embodiment, the outer surface Shore D hardnessH_(outer surface)+30—the center Shore C hardness H_(center)≧about 85.

The inner core layer meanwhile has an inner core interface Shore Chardness (H_(inner core interface)). The inner core layer has a negativehardness gradient wherein the inner core interface Shore C hardness(H_(inner core interface)) is less than the center Shore C hardness, ora zero hardness gradient wherein the inner core interface Shore Chardness (H_(inner core interface)) is within 1 Shore C unit of thecenter Shore C hardness, or positive hardness gradient wherein innercore interface Shore C hardness (H_(inner core interface)) is greaterthan the center Shore C hardness.

The inner core layer may have an overall zero hardness gradient betweencenter Shore C hardness (H_(center)) and interface Shore C hardness(H_(inner core interface)), whereinH_(inner core interface)=(H_(center)). Or, in another embodiment,−1<H_(inner core interface)−H_(center)<1. In yet another embodiment, theinner core layer may have a positive hardness gradient between centerShore C hardness (H_(center)) and interface Shore C hardness(H_(inner core interface)) wherein:

1<H _(inner core interface) −H _(center)<45,

or 1<H _(inner core interface) −H _(center)<15,

or 1<H _(inner core interface) −H _(center)<5.

For example, in one embodiment, 1<H_(inner core interface)−H_(center)≦5.In another embodiment, 2<H_(inner core interface)−H_(center)≦5. In yetanother embodiment, 3<H_(inner core interface)−H_(center)≦5. In analternative embodiment, 4<H_(inner core interface)−H_(center)≦5.

In other embodiments, the inner core layer may have an overall negativehardness gradient. For example, in one embodiment,−1>H_(inner core interface)−H_(center)≧5.

In one embodiment, the outer core layer has an outer core interfaceShore D hardness (H_(outer core interface)) such that the Shore DH_(outer core interface)−the Shore C H_(inner core interface)≦the ShoreD H_(outer surface)−the Shore C H_(center). This occurs, for example,where: (i) the Shore C H_(inner core interface)>the Shore C H_(center),and the Shore D H_(outer core interface)=the Shore D H_(outer surface);(ii) the Shore C H_(inner core interface)=the Shore C H_(center), andthe Shore D H_(outer core interface)<the Shore D H_(outer surface);(iii) the Shore C H_(inner core interface)>the Shore C H_(center), andthe Shore D H_(outer core interface)<the Shore D H_(outer surface);and/or (iv) the Shore C H_(inner core interface)=the Shore C H_(center),and the Shore D H_(outer core interface)=the Shore D H_(outer surface).

A non-limiting example of (i) is where the Shore DH_(outer core interface) (55)−the Shore C H_(inner core interface)(50)≦the Shore D H_(outer surface) (55)−the Shore C H_(center)(45)_(.)In turn, an example of (ii) is where the Shore DH_(outer core interface) (50)−the Shore C H_(inner core interface)(50)≦the Shore D H_(outer surface) (55)−the Shore C H_(center)(50). Andan example of (iii) is where the Shore D H_(outer core interface)(50)−the Shore C H_(inner core interface) (55)≦the Shore DH_(outer surface) (55)−the Shore C H_(center)(50). Finally, one exampleof (iv) is where the Shore D H_(outer core interface) (55)−the Shore CH_(inner core interface) (50)=the Shore D H_(outer surface)+(55)−theShore C H_(center)(50).

In another embodiment, the outer core layer has an outer core interfaceShore D hardness (H_(outer core interface)) such that the Shore DH_(outer core interface)−the Shore CH_(inner core interface)>H_(outer surface)−H_(center). This occurs, forexample, where: (v) the Shore C H_(inner core interface)<the Shore CH_(center), and the Shore D H_(outer core interface)=the Shore DH_(outer surface); (vi) the Shore C H_(inner core interface)=the Shore CH_(center), and the Shore D H_(outer core interface)>the Shore DH_(outer surface); or (vii) the Shore C H_(inner core interface)<theShore C H_(center), and the Shore D H_(outer core interface)>the Shore DH_(outer surface).

A non-limiting example of (v) is where the Shore DH_(outer core interface) (55)−the Shore C H_(inner core interface) (45Shore C)>the Shore D H_(outer surface) (55)−the Shore CH_(center)(50).In turn, an example of (vi) is where the Shore DH_(outer core interface) (60)−the Shore C H_(inner core interface)(50)>the Shore D H_(outer surface) (55)−the Shore C H_(center)(50). Andan example of (vii) is where the Shore D H_(outer core interface)(65)−the Shore C H_(inner core interface) (45)>the Shore DH_(outer surface) (55)−the Shore C the Shore C H_(center)(50).

Non-limiting examples of suitable thermoplastic compositions for TP₁include at least one of ionomers; non-ionomeric acid polymers;polyurethanes, polyureas, and polyurethane-polyurea hybrids;polyester-based thermoplastic elastomers; polyamides, copolymers ofionomer and polyamide, polyamide-ethers, and polyamide-esters;ethylene-based homopolymers and copolymers; propylene-based homopolymersand copolymers; triblock copolymers based on styrene andethylene/butylene; derivatives thereof that are compatibilized with atleast one grafted or copolymerized functional group; and combinationsthereof.

Embodiments are also envisioned wherein outer core layer TP₂ furthercomprises (in addition to the at least one transparent or plasticizedpolyamide) at least one thermoplastic material being a primarilyionomeric material, or HNP. In a different embodiment, the outer corelayer TP₂ may further comprise (in addition to the at least onetransparent or plasticized polyamide) at least one thermoplasticmaterial comprising a stiff thermoplastic polyurethane material.

In one non-limiting embodiment, the core includes an intermediate corelayer formed from a thermoset rubber-based composition. Suitablethermoset compositions include, for example, a rubber-based compositioncomprising at least one of natural rubber, polybutadiene, polyisoprene,ethylene propylene rubber (EPR), ethylene-propylene-diene rubber (EPDM),styrene-butadiene rubber, butyl rubber, halobutyl rubber, polyurethane,polyurea, acrylonitrile butadiene rubber, polychloroprene, alkylacrylate rubber, chlorinated isoprene rubber, acrylonitrile chlorinatedisoprene rubber, polyalkenamer, phenol formaldehyde, melamineformaldehyde, polyepoxide, polysiloxane, polyester, alkyd,polyisocyanurate, polycyanurate, polyacrylate, and combinations thereof.

Inner Core Layer Formed From a Thermoplastic Composition, Outer CoreLayer Formed From a Thermoset Composition; & Inner Core Layer FormedFrom a Thermoplastic Composition, Outer Core Layer Formed FromThermoplastic Composition different than that of the Inner Core Layer

In another different construction, the invention is directed to a golfball comprising a core and a cover. The core consists of an inner corelayer, one or more optional intermediate core layers, and an outer corelayer. The inner core layer is a solid layer formed from an unfoamedthermoplastic composition, and has a diameter of 1.10 inch or less and acenter Shore C hardness (H_(center)) of 50 or less. The outer core layeris formed from a thermoset composition, has a thickness of 0.200 inchesor greater, and an outer surface Shore C hardness (H_(ouser surface)) of70 or greater. The outer surface hardness of the outer core layer is atleast 40 Shore C points greater than the center hardness of the innercore layer.

In a further differing construction, the invention is directed to a golfball comprising a core and a cover. The core consists of an inner corelayer, one or more optional intermediate core layers, and an outer corelayer. The inner core layer is a solid layer formed from an unfoamedfirst thermoplastic composition TP₁, and has a diameter of 1.10 inch orless and a center Shore C hardness (H_(center)) of 50 or less. The outercore layer is formed from a second thermoplastic composition TP₂, has athickness of 0.200 inches or greater, and an outer surface Shore Chardness (H_(outer surface)) of 70 or greater. The outer surfacehardness of the outer core layer is at least 40 Shore C points greaterthan the center hardness of the inner core layer.

H_(center) may alternatively be 45 or less, or 40 or less, or less than40, or 35 or less, or less than 35, or 30 or less, or less than 30, or25 or less or less than 25, or 20 or less, or less than 20, or 15 orless, or less than 15, or 13 or less, or less than 13, or a Shore Chardness within a range having a lower limit of 5 or 10 and an upperlimit of 15 or 25 or 30 or 35 or 40.

The inner core layer may alternatively have a diameter of less than 1.10inches, or 1.00 inches or less, or less than 1.00 inches, or 0.90 inchesor less, or less than 0.90 inches, or 0.80 inches or less, or less than0.80 inches, or 0.75 inches or less, or less than 0.75 inches, or adiameter within a range having a lower limit of 0.10 or 0.15 or 0.20 or0.25 or 0.30 or 0.35 or 0.40 or 0.45 or 0.50 or 0.55 inches and an upperlimit of 0.60 or 0.65 or 0.70 or 0.75 or 0.80 or 0.85 or 0.90 or 0.95 or1.00 or 1.05 or 1.10 inches.

The inner core layer has an inner core outer surface having a Shore Chardness (H_(icos)) that differs from H_(center) by up to 5 Shore C. Inanother embodiment, H_(icos) and H_(center) differ by up to about 5Shore C. In one embodiment, H_(center) is greater than H_(icos) by up to5 Shore C. In another embodiment, H_(center) is less than H_(icos) by upto 5 Shore C. In other embodiments, H_(center) is greater than H_(icos)by up to 4 Shore C, or by up to 3 Shore C, or by up to 2 Shore C, or byless than 2 Shore C. Alternatively, H_(center) may be less than H_(icos)by up to 4 Shore C, or by up to 3 Shore C, or by up to 2 Shore C, or byless than 2 Shore C. In one embodiment, H_(center) and H_(icos) aresubstantially the same.

H_(outer surface) may alternatively be 75 or greater, or 70 or greater,or greater than 70, or 75 or greater, or greater than 75, 80 or greater,or greater than 80, or 85 or greater, or greater than 85, or 87 orgreater, or greater than 87, or 89 or greater, or greater than 89, or 90or greater, or greater than 90, or 91 or greater, or greater than 91, or92 or greater, or greater than 92, or a Shore C hardness within a rangehaving a lower limit of 80 or 85 or 87 or 89 and an upper limit of 90 or91 or 92 or 95.

In one embodiment, H_(outer surface) is greater than an outer core layerinner surface Shore C hardness (H_(inner surface)) by greater than 30.In another embodiment, H_(outer surface) is greater thanH_(inner surface) by from 10 to 30. In yet another embodiment,H_(ower surface) is greater than H_(inner surface) by less than 10.

The outer core layer may alternatively have a thickness of greater than0.10 inches, or 0.20 inches or greater, or greater than 0.20 inches, or0.30 inches or greater, or greater than 0.30 inches, or 0.35 inches orgreater, or greater than 0.35 inches, or 0.40 inches or greater, orgreater than 0.40 inches, or 0.45 inches or greater, or greater than0.45 inches, or a thickness within a range having a lower limit of 0.005or 0.010 or 0.015 or 0.020 or 0.025 or 0.030 or 0.035 or 0.040 or 0.045or 0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090or 0.100 or 0.200 or 0.250 inches and an upper limit of 0.300 or 0.350or 0.400 or 0.450 or 0.500 inches.

In another embodiment, H_(outer surface)−H_(center)≧45. In yet anotherembodiment, H_(outer surface)−H_(center)≧50. In still anotherembodiment, H_(outer surface)−H_(center)≧55. In an alternativeembodiment, H_(outer surface)−H_(center)>55. In a different embodiment,H_(outer surface)−H_(center)≧60. In other embodiments,H_(outer surface)−H_(center)>60, or H_(outer surface)−H_(center)≧65, orH_(outer surface)−H_(center)>65, or H_(outer surface)−H_(center)>70, orH_(outer surface)−H_(center)>70, or H_(outer surface)−H_(center)≧75, orH_(outer surface)−H_(center)>75, or H_(outer surface)−H_(center)≧80, orH_(outer surface)−H_(center)>80.

Additionally, the inner core layer has an inner core interface Shore Chardness (H_(inner core interface))—See, e.g., FIG. 1 and discussionbelow relating to FIG. 1.

The inner core layer has a negative hardness gradient wherein theinterface Shore C hardness of the inner core layer is less than thecenter Shore C hardness, or a zero hardness gradient wherein theinterface Shore C hardness of the inner core layer is within 1 Shore Cunit of the center Shore C hardness, or positive hardness gradientwherein the interface Shore C hardness of the inner core layer isgreater than the center Shore C hardness.

In a particular embodiment, the inner core layer has a center Shore Chardness (H_(center)) within a range having a lower limit of 1 or 5 or10 and an upper limit of 15 or 25 or 30 or 35 or 40 and an interfaceShore C hardness (H_(inner core interface)) within a range having alower limit of 5 or 10 or 15 and an upper limit of 15 or 20 or 25 or 30or 35 or 40 or 50, and has an overall zero hardness gradient whereinH_(inner core interface)=H_(center) orwherein-1<H_(inner core interface)−H_(center)<1; or a positive hardnessgradient wherein:

1<H _(inner core interface) −H _(center)<45,

or 1<H _(inner core interface) −H _(center)<15,

or 1<H _(inner core interface) −H _(center)<5.

For example, in one embodiment, 1<H_(inner core interface)−H_(center)≦5.In another embodiment, 2<H_(inner core interface)−H_(center)≦5. In yetanother embodiment, 3<H_(inner core interface)−H_(center)≦5. In analternative embodiment, 4<H_(inner core interface)−H_(center)≦5.

In other embodiments, the inner core layer may have an overall negativehardness gradient. For example, in oneembodiment,-1>H_(inner core interface)−H_(center)≧−5. In yet anotherembodiment,−2>H_(inner core interface)−H_(center)≧−5. In still anotherembodiment, -3>H_(inner core interface)−H_(center)≧−5. In a differentembodiment, −4>H_(inner core interface)−H_(center)≧−5.

In one embodiment, the outer core layer has an outer core interfaceShore C hardness (H_(outer core interface)) such thatH_(outer core interface)−H_(inner core interface)≦H_(outer surface)−H_(center).This occurs, for example, where: (i)H_(inner core interface)>H_(center), andH_(outer core interface)=H_(outer surface); (ii)H_(inner core interface)=H_(center), andH_(outer core interface)<H_(outer surface);(iii)H_(inner core interface)>H_(center), andH_(outer core interface)<H_(outer surface); and/or (iv)H_(inner core interface)=H_(center), andH_(outer core interface)=H_(outer surface).

A non-limiting example of (i) is where H_(outer core interface) (85Shore C)−H_(inner core interface) (50 Shore C)>H_(outer surface)(85Shore C)−H_(center)(45 Shore C). In turn, an example of (ii) is whereH_(outer core interface) (80 Shore C)−H_(inner core interface) (50 ShoreC)≦H_(outer surface)(⁸⁵ Shore C)−H_(center)(50 Shore C). And an exampleof (iii) is where H_(outer core interface) (80 ShoreC)−H_(inner core interface) (55 Shore C)≦H_(ou)t_(er surface)(85 ShoreC)−H_(center)(50 Shore C). Finally, one example of (iv) is whereH_(outer core interface) (85 Shore C)−H_(inner core interface) (50 ShoreC)=H_(outer surface)(85 Shore C)−H_(center)(50 Shore C).

In another embodiment,H_(outer core interface)−H_(inner core interface)>H_(outer surface)−H_(center).This occurs, for example, where: (v)H_(inner core interface)<H_(center), andH_(outer core interface)=H_(outer surface); (vi)H_(inner core interface)=H_(center), andH_(outer core interface)>H_(outer surface); or(Vii)H_(inner core interface)<H_(center) andH_(outer core interface)>H_(outer surface).

A non-limiting example of (v) is where H_(outer core interface) (terface 85 Shore C)−H_(inner core interface) (45 ShoreC)>H_(outer surface)(85 Shore C)−H_(center)(50 Shore C). In turn, anexample of (vi) is where H_(outer core interface) (85 ShoreC)−H_(inner core interface) (50 Shore C)>H_(outer surface)(80 ShoreC)−H_(center)(₅₀ Shore C). And an example of (vii) is whereH_(outer core interface) ( terface 85 Shore C)−H_(inner core interface)(45 Shore C)>H_(outer surface)( 80 Shore C)−H_(center)(50 Shore C).

Non-limiting examples of suitable thermoplastic compositions include atleast one of ionomers; non-ionomeric acid polymers; polyurethanes,polyureas, and polyurethane-polyurea hybrids; polyester-basedthermoplastic elastomers; polyamides, copolymers of ionomer andpolyamide, polyamide-ethers, and polyamide-esters; ethylene-basedhomopolymers and copolymers; propylene-based homopolymers andcopolymers; triblock copolymers based on styrene and ethylene/butylene;derivatives thereof that are compatibilized with at least one grafted orcopolymerized functional group; and combinations thereof. In theconstruction incorporating TP₁ and TP₂, the thermoplastic compositionsfor the inner core layer and outer core layer may in one embodiment havethe same classification- e.g. each being a primarily iomomeric material,or HNP. In a different embodiment, the thermoplastic compositions forthe inner core layer and outer core layer may have differentclassifications- e.g., the inner core layer comprising a primarilyiomomeric material, whereas the outer core layer comprises a stiffthermoplastic polyurethane material.

In the construction incorporating a thermoset outer core layercomposition, suitable thermoset compositions include, for example, arubber-based composition comprising at least one of natural rubber,polybutadiene, polyisoprene, ethylene propylene rubber (EPR),ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber, butylrubber, halobutyl rubber, polyurethane, polyurea, acrylonitrilebutadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinatedisoprene rubber, acrylonitrile chlorinated isoprene rubber,polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide,polysiloxane, polyester, alkyd, polyisocyanurate, polycyanurate,polyacrylate, and combinations thereof.

Optional intermediate core layers are disposed between the inner corelayer and outer core layer and have an individual layer thickness withina range having a lower limit of 0.005 or 0.010 or 0.015 or 0.020 or0.025 or 0.030 or 0.035 or 0.040 or 0.045 inches and an upper limit of0.050 or 0.055 or 0.060 or 0.065 or 0.070 or 0.075 or 0.080 or 0.090 or0.100 or 0.150 or 0.200 or 0.250 or inches. In one non-limitingembodiment, the core includes an intermediate layer formed from a rubbercomposition. In another non-limiting embodiment, the core includes anintermediate layer formed from an HNP composition. A core intermediatelayer may have a hardness in the range of from about 10 Shore C to about90 Shore C.

The multilayer core has an overall diameter of 1.00 inch or greater, or1.20 inches or greater, or 1.25 inches or greater, or 1.30 inches orgreater, or 1.35 inches or greater, or 1.40 inches or greater, or 1.45inches or greater, or 1.50 inches or greater, or 1.51 inches or greater,or 1.53 inches or greater, or 1.55 inches or greater, or an overalldiameter within a range having a lower limit of 0.50 or 0.70 or 0.75 or0.80 or 0.85 or 0.90 or 0.95 or 1.00 or 1.10 or 1.15 or 1.20 or 1.25 or1.30 or 1.35 or 1.40 or 1.45 or 1.50 or 1.51 or 1.53 or 1.55 and anupper limit of 1.55 or 1.60 or 1.61 or 1.62 or 1.63 or 1.64 inches.

The inner core layer has a compression of 40 or less, or 30 or less, or25 or less, or less than 25, or 20 or less, or less than 20, or 15 orless, or less than 15, or 10 or less, or less than 10, or 5 or less, orless than 5, or 0 or less, or less than 0. Meanwhile, the core has anoverall compression of 50 or greater, or 60 or greater, or 65 orgreater, or 70 or greater, or 80 or greater, or greater than 80, or 85or greater, or greater than 85, or 90 or greater, or an overallcompression within a range having a lower limit of 50 or 60 or 65 or 70or 80 or 85 and an upper limit of 90 or 95 or 100 or 110. The inner corelayer has a coefficient of restitution (“COR”) at 125 ft/s of 0.780 orless, or 0.650 or less, or 0.600 or less, or 0.550 or less, and themultilayer core has an overall COR of 0.795 or greater, or 0.800 orgreater, or 0.810 or greater, or 0.815 or greater, or 0.820 or greater.

Golf balls of the present invention typically have a COR of 0.700 orgreater, preferably 0.750 or greater, and more preferably 0.780 orgreater. Golf balls of the present invention typically have acompression of 40 or greater, or a compression within a range having alower limit of 50 or 60 and an upper limit of 100 or 120.

In one embodiment, a golf ball of the invention incorporates anintermediate layer (or inner cover layer) between the core and the cover(or between the core and outer cover layer). In such an embodiment, theintermediate layer or inner cover layer, formed about the core, has asurface hardness of from about 50 Shore D to about 80 Shore D.

The finished golf ball has a compression that is greater than acompression of the inner core layer and outer core layer, combined. Inone embodiment, the compression of the finished golf ball is greaterthan the compression of the inner core layer and outer core layer,combined, by at least 10%. In another embodiment, the compression of thefinished golf ball is greater than the compression of the inner corelayer and outer core layer, combined, by at least 15%. In yet anotherembodiment, the compression of the finished golf ball is greater thanthe compression of the inner core layer and outer core layer, combined,by at least 20%, or by at least 25%, or by at least 30%, or by at least35%, or by at least 40%, or by at least 50%, or by at least 55%, or byabout 60% or greater.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a graph depicting core hardness as a function of distance fromthe center and further depicting extrapolated interfaces for the innerand outer core layers according to one embodiment of a golf ball of theinvention.

DETAILED DESCRIPTION

Several embodiments of a golf ball of the invention incorporating aninner core layer formed from a thermoplastic composition and an outercore layer formed from a thermoset Composition are illustrated inprophetic golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4 and compared withone conventional prophetic golf ball Comp. Ex. 1. In this regard, atleast one core layer in each of golf balls Ex. 1, Ex. 2, Ex. 3, Ex. 4and Comp. Ex. 1 includes at least one of the rubber-based formulas setforth in TABLE I as follows:

TABLE I THERMOSET CORE MATERIALS INGREDIENTS Core Core Core (Phr)Formulation 1 Formulation 2 formulation 3 Polybutadiene 100 100 100 ZincOxide 5 5 5 Zinc diacrylate (ZDA) 35 38 31 Perkadox ® BC¹ 0.5 0.5 *Trigonox ® 265² * * 1 Antioxidant * * 0.4 ZnPCTP 0.5 0.5 0.5 ¹Perkadox ®BC is an initiating agent (Dicumyl peroxide) available from Akzo Nobel.²Trigonox ® 265 is an initiating agent available from Akzo Nobel.

TABLE II below details the construction and certain properties forprophetic golf balls Ex. 1, Ex. 2, Ex. 3, Ex. 4 and Comp. Ex. 1:

TABLE II Golf Ball Construction EXAMPLES & Properties Ex. 1 Ex. 2 Ex. 3Ex. 4 Comp. Ex. 1 Inner Core Pebax ® Kraton ® Estane ® Elvax ® CoreMaterial 2533 SA 01³ D1101 K⁴ T370A TPU⁵ 40W⁶ Formulation 3⁷ Inner Core 0.75  0.50 0.75 0.50 1.00 Diameter (in.) Center Hardness 47.6  29.2 36.4 12.5 71.0 (Shore C) Inner Core ≦40     ≦40     ≦40 ≦40 >40Compression Outer Core Core Core Core Core Core Material FormulationFormulation Formulation Formulation Formulation  1⁷    2⁷   1 2 1 OuterCore  0.400  0.525 0.400 0.525 0.275 Thickness (in.) Outer Core Surf.87.9  88.6  88.1 89.2 87.5 Hardness (Shore C) Dual Core 77   68   65 5288 Compression Intermediate Surlyn ® Surlyn ® Surlyn ® Surlyn ® Surlyn ®Layer Material 7940/8940⁸ 7940/8940 7940/8940 7940/8940 7940/8940Intermediate  0.035  0.035 0.035 0.035 0.035 Layer Thickness (in.)Intermediate 69.1  68.8  68.8 68.9 69.3 Layer Hardness (Shore D) CoverMaterial MDI⁹/ MDI/ MDI/ MDI/ MDI/ PTMEG¹⁰/ PTMEG/ PTMEG/ PTMEG/ PTMEG/E-300¹¹ E-300 E-300 E-300 E-300 Cover Thickness  0.030  0.030 0.0300.030 0.030 (in.) Cover Hardness 82.1  81.9  82.0 82.2 82.1 (Shore C)Ball 86   78   76 61 99 Compression ³Pebax ®2533 SA 01 is athermoplastic elastomer formed from flexible polyether and rigidpolyamide, available from ARKEMA (polyether amide). ⁴Kraton ®D1101 K isa linear triblock copolymer based on styrene and butadiene, with astyrene content of 31%, available from KRATON Polymers Group (styreneblock copolymer). ⁵Estane ®T370 A is a thermoplastic polyurethaneavailable from Lubrizol. ⁶Elvax ®40W is an ethylene vinyl acetatecopolymer resin available from DuPont (EVA). ⁷Core Formulations 1, 2 & 3are set forth in TABLE I above. ⁸Surlyn ®7940 (Li) and Surlyn ®8940(Na), are medium acid, monovalent and medium flow ionomers. ⁹Methylenediphenyl diisocyanate. ¹⁰Polytetramethylene ether glycol. ¹¹Ethacure300, dimethylthiotoluene diamine, sold by Albemarle.

As evident from TABLE I, core formulations 1, 2 & 3 differ from eachother in at least one of the amount of peroxide, the amount of zincdiacrylate, and presence/absence of an antioxidant.

Referring to golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4 of TABLE II, eachincorporates a dual core comprising a very soft, low compression innercore layer surrounded by a hard higher compression thermoset outer corelayer. Additionally, each inner core layer has a diameter of less than1.10 inches, is formed from an unfoamed thermoplastic composition, andhas a center Shore C hardness of 50 or less. Meanwhile, each outer corelayer has a thickness of 0.200 inches or greater, is formed from athermoset composition, and has an outer surface Shore C hardness of 80or greater. Finally, in each of the dual cores of golf balls Ex. 1, Ex.2, Ex. 3, and Ex. 4, the outer core layer has an outer surface hardnessthat is at least 40 Shore C points greater than the center hardness ofthe inner core layer.

Specifically referring to golf ball Ex. 1, the inner core layer has adiameter of 0.75 in., is formed from a polyether amide, and has a centerShore C hardness of 47.6. The outer core layer meanwhile has a thicknessof 0.400 in., is formed from core formulation 1, and has an outersurface Shore C hardness of 87.9. The outer surface hardness of theouter core layer of golf ball Ex. 1 is therefore “at least 40 Shore Cpoints greater than the center hardness of the inner core layer” (namely40.3 Shore C points greater than the center hardness).

Golf ball Ex. 3′s construction/composition is different than that golfball Ex. 1 in that the inner core layer of Ex. 3 is formed from athermoplastic polyurethane rather than a polyether amide. Severalproperty differences may also be noted between golf balls Ex. 3 and Ex.1, respectively: inner core layer center Shore C hardnesses (36.4 versus47.6); outer core layer surface Shore C hardnesses (88.1 versus 87.9);dual core compressions (65 versus 77); intermediate layer Shore Dhardnesses (68.8 versus 69.1); cover layer surface shore C hardness(82.0 versus 82.1); and golf ball compression (76 versus 86).Nevertheless, golf ball Ex. 3 has an outer core layer outer surfacehardness that is greater than the center hardness of the inner corelayer by 51.7 Shore C hardness points, which is well above “at least 40Shore C points greater”.

In turn, golf ball Ex. 4′s construction/composition is different thanthat of golf ball Ex. 2 in that the inner core layer of Ex. 4 is formedfrom an EVA rather than a styrene block copolymer. Several propertydifferences may also be noted between golf balls Ex. 4 and Ex. 2,respectively: inner core layer center Shore C hardnesses (12.5 versus29.2); outer core layer surface Shore C hardnesses (89.2 versus 88.6);dual core compressions (52 versus 68); intermediate layer Shore Dhardnesses (68.9 versus 68.8); cover layer surface shore C hardness(82.2 versus 81.9); and golf ball compression (61 versus 78). Yet bothgolf balls Ex. 2 and Ex. 4 have a very high positive hardness gradientwherein the outer surface hardness of the outer core layer is at least40 Shore C points greater than the center hardness of the inner corelayer, namely by 59.4 and 76.7 Shore C hardness points, respectively.

Comparative golf ball Comp. Ex. 1, in contrast to golf balls Ex. 1, Ex.2, Ex. 3, and Ex. 4, is formed from a conventional thermosetrubber-based composition having a center Shore C hardness well above 50(namely 71). Additionally, Comp. Ex. 1 incorporates an outer core layerhaving an outer surface Shore C hardness that is not “at least 40 ShoreC points greater than the center hardness of the inner core layer” butrather, well below that, namely only 16.5 Shore C points greater.

Accordingly, each of golf balls Ex. 1, Ex. 2, Ex. 3, and Ex. 4incorporates a core having a steep positive Shore C hardness gradientprogressing from a hard core outer surface to a very soft center,whereas the core of golf ball Comp. Ex. 1 has a center Shore C hardnessabove 50 and a much more shallow Shore C hardness gradient from outersurface to center and well below “at least 40”.

Several different constructions incorporating an inner core layer formedfrom a thermoplastic composition and an outer core layer formed from athermoplastic composition different than that of the inner corecomposition are illustrated in prophetic golf balls Ex. 5, Ex. 6, Ex. 7,and Ex. 8 and compared with one conventional prophetic golf ball Comp.Ex. 2 herein below.

Prophetic inventive golf balls Ex. 5, Ex. 6, Ex. 7, Ex. 8 andcomparative prophetic golf ball Comp. Ex. 2 each comprise a core, acover, and an intermediate layer disposed between the core and thecover. Additionally, every core is a dual core comprising an inner corelayer surrounded by an outer core layer.

The inner core layers of inventive prophetic golf balls Ex. 5, Ex. 6,Ex. 6, and Ex. 7 are each formed from a different thermoplasticmaterial, namely Elvax®150 (ethylene-vinyl acetate copolymer (EVA)),Nucrel®9-1(olefin-unsaturated carboxylic acid ester terpolymer), Kraton®D0243 B(styrene block copolymer), and Riteflex®425(thermoplasticpolyester elastomer), respectively. In turn, the outer core layers ofgolf balls Ex. 5, Ex. 6, Ex. 7, and Ex. 8 are also each formed from adifferent thermoplastic composition as formulated in TABLE III:

TABLE III OUTER CORE LAYER MATERIALS (TP₂) Ingredients Ex. 5 Ex. 6 Ex. 7Ex. 8 (Phr) TP₂(1) TP₂(2) TP₂(3) TP₂(4) Primacor ® 5980I¹² 43 48 48 47Fusabond ® N525¹³ 11 * 12 * Elvaloy ® AC 3427¹⁴ * * * 13 Kraton FG1924G¹⁵ * 12 * * Ethyl Oleate 10 * * * Oleic Acid 36 40 40 40 Mg(OH)₂ 8.08.9 8.9 8.8 ¹²Primacor ® 5980I is an Ethylene/-Acrylic Acid Copolymeravailable from Dow Chemical Company. ¹³Fusabond ® N525 is an anhydridemodified ethylene copolymer available from E. I. du Pont de Nemours andCompany, Inc. ¹⁴Elvaloy ® AC 3427 is a copolymer of ethylene and butylacrylate available from E. I. du Pont de Nemours and Company, Inc.¹⁵Kraton FG1924 G is a linear triblock copolymer based on styrene andethylene/butylene with a polystyrene content of 13% (Styrene blockcopolymer) available from Kraton Polymers.

Meanwhile, in comparative golf ball Comp. Ex. 2, both the inner corelayer and outer core layer are formed from conventional thermosetrubber-based compositions as formulated in TABLE IV below. As shown inTABLE IV, core formulations 1 and 2 differ from each other at least bythe amount of peroxide, the amount of zinc diacrylate, andpresence/absence of an antioxidant:

TABLE IV GOLF BALL COMP. EX. 2 CORE LAYERS MATERIALS Ingredients OUTERCORE LAYER INNER CORE LAYER (Phr) (Core Formulation 1) (Core formulation2) Polybutadiene 100 100 Zinc Oxide 5 5 Zinc diacrylate (ZDA) 35 31Perkadox ® BC¹⁶ 0.5 * Trigonox ® 265¹⁷ * 1 Antioxidant * 0.4 ZnPCTP 0.50.5 ¹⁶Perkadox ® BC is an initiating agent (Dicumyl peroxide) availablefrom Akzo Nobel. ¹⁷Trigonox ®265 is an initiating agent available fromAkzo Nobel.

TABLE V incorporates the details of TABLE III and TABLE IV therein andfurther specifies the construction and certain additional properties foreach of golf balls Ex. 5, Ex. 6, Ex. 7, Ex. 8 and Comp. Ex. 2:

TABLE V Golf Ball Construc- EXAMPLES tion & Comp. Properties Ex. 5 Ex. 6Ex. 7 Ex. 8 Ex. 2 Inner Core Elvax ® Nucrel ® Kraton ® Riteflex ® CoreMaterial 150¹⁸ 9-1¹⁹ D0243 425²¹ Formu- B²⁰ lation 2²² Inner Core 0.750.50 0.75 0.50 1.00 Diameter (in.) Center 26.8 48.6 35.5 43.3 71.0Hardness (Shore C) Inner Core ≦40 ≦40 ≦40 ≦40 >40 Com- pression OuterCore TP₂ (1) TP₂ (2) TP₂ (3) TP₂ (4) Core Material Formu- lation 1²²Outer Core 0.400 0.525 0.400 0.525 0.275 Thickness (in.) Outer 84.5 91.591.1 88.6 87.5 Core Surf. Hardness (Shore C) Dual Core 65 98 69 89 88Com- pression Intermedi- Surlyn® Surlyn® Surlyn® Surlyn® Surlyn ® ateLayer 7940/8940²³ 7940/ 7940/ 7940/ 7940/ Material 8940 8940 8940 8940Intermedi- 0.035 0.035 0.035 0.035 0.035 ate Layer Thickness (in.)Intermedi- 68.9 69.1 69.2 69.5 69.3 ate Layer Hardness (Shore D) CoverMDI²⁴/ MDI/ MDI/ MDI/ MDI/ Material PTMEG²⁵/ PTMEG/ PTMEG/ PTMEG/ PTMEG/E-300²⁶ E-300 E-300 E-300 E-300 Cover 0.030 0.030 0.030 0.030 0.030Thickness (in.) Cover 82.3 82.5 81.9 82.2 82.1 Hardness (Shore C) Ball72 110 79 91 99 Com- pression ¹⁸Elvax ®150 is an ethylene-vinyl acetatecopolymer resin (EVA) available from E. I. du Pont de Nemours andCompany, Inc. ¹⁹Nucrel®9-1 is an olefin-unsaturated carboxylic acidester terpolymer available from E. I. du Pont de Nemours and Company,Inc. ²⁰Kraton® D0243 B is a diblock copolymer based on styrene andbutadiene with a polystyrene content of 33% (styrene block copolymer)available from Kraton Polymers. ²¹Riteflex® 425 is a thermoplasticpolyester elastomer available from Ticona. ²²Core Formulations 1&2 asset forth in TABLE III above. ²³Surlyn® 7940 (Li) and Surlyn ®8940 (Na),are medium acid, monovalent and medium flow ionomers. ²⁴Methylenediphenyl diisocyanate. ²⁵Polytetramethylene ether glycol. ²⁶Ethacure300, dimethylthiotoluene diamine, sold by Albemarle.

Referring to golf balls Ex. 5, Ex. 6, Ex. 7, and Ex. 8 of TABLE V, eachdual core comprises a very soft, low compression inner core layersurrounded by a hard higher compression outer core layer. Additionally,each inner core layer has a diameter of less than 1.10 inches, is formedfrom an unfoamed thermoplastic composition, and has a center Shore Chardness of 50 or less.

Meanwhile, each outer core layer has a thickness of 0.200 inches orgreater, is formed from a second thermoplastic composition that isdifferent than the thermoplastic material of the inner core layer, andhas an outer surface Shore C hardness of 80 or greater. Finally, in eachof the dual cores of golf balls Ex. 5, Ex. 6, Ex. 7, and Ex. 8, theouter core layer has an outer surface hardness that is at least 40 ShoreC points greater than the center hardness of the inner core layer.

Specifically referring to golf ball Ex. 5, the EVA inner core layer hasa diameter of 0.75 in., and has a center Shore C hardness of 26.8. Theouter core layer meanwhile has a thickness of 0.400 in., is formed fromcore formulation TP₂(1), and has an outer surface Shore C hardness of84.5. The outer surface hardness of the outer core layer of golf ballEx. 5 is therefore “at least 40 Shore C points greater than the centerhardness of the inner core layer” (namely 57.7 Shore C points greaterthan the center hardness).

Notably, in golf ball Ex. 7, TP₂(3) differs from TP₂(1) of golf ball Ex.5 at least in that TP₂(1) includes ethyl oleate, whereas TP₂(3) doesnot. Several property differences may also be noted between golf ballsEx. 7 and Ex. 5, respectively: inner core layer center Shore Chardnesses (35.5 versus 26.8); outer core layer surface Shore Chardnesses (91.1 versus 84.5); dual core compressions (69 versus 65);intermediate layer Shore D hardnesses (69.2 versus 68.9); cover layersurface shore C hardness (81.9 versus 82.3); and golf ball compression(79 versus 72). Nevertheless, golf ball Ex. 7 has an outer core layerouter surface hardness that is greater than the center hardness of theinner core layer by 55.6 Shore C hardness points, which is well above“at least 40 Shore C points greater”. Property difference between golfballs Ex. 7 and Ex. 5 may be attributed to the outer core layerformulation differences between TP₂(3) and TP₂(1) as well to the innercore material difference (styrene block copolymer versus EVA).

Regarding golf ball Ex. 8, it is also notable that TP₂(4) differs fromTP₂(2) of golf ball Ex. 6 at least in that TP₂(4) includes a copolymerof ethylene and butyl acrylate, whereas TP₂(2) includes a styrene blockcopolymer instead. Several property differences may also be notedbetween golf balls Ex. 8 and Ex. 6, respectively: inner core layercenter Shore C hardnesses (43.3 versus 48.6); outer core layer surfaceShore C hardnesses (88.6 versus 91.5); dual core compressions (89 versus98); intermediate layer Shore D hardnesses (69.5 versus 69.1); coverlayer surface shore C hardness (82.2 versus 82.5); and golf ballcompression (91 versus 110). Yet both golf balls Ex. 6 and Ex. 8 have avery high positive hardness gradient wherein the outer surface hardnessof the outer core layer is at least 40 Shore C points greater than thecenter hardness of the inner core layer, namely by 42.9 and 45.7 Shore Chardness points, respectively. Once again, property difference betweengolf balls Ex. 8 and Ex. 6 may be attributed to the outer layerformulation difference between TP₂(4) and TP₂(2) as well as to thediffering inner core materials (thermoplastic polyester elastomer versusolefin-unsaturated carboxylic acid ester terpolymer).

Comparative golf ball Comp. Ex. 2, unlike golf balls Ex. 5, Ex. 6, Ex.7, and Ex. 8, incorporates conventional thermoset rubber-basedcompositions in both the inner core layer and an outer core layer. Theinner core layer of Comp. Ex. 2 is formed from a conventional thermosetrubber-based composition having a center Shore C hardness well above 50(namely 71). Meanwhile, the outer core layer of Comp. Ex. 2 has an outersurface Shore C hardness that is not “at least 40 Shore C points greaterthan the center hardness of the inner core layer” but rather, well belowthat, namely only 16.5 Shore C points greater. Furthermore,

Accordingly, each of golf balls Ex. 5, Ex. 6, Ex. 7, and Ex. 8incorporates a core having a steep positive Shore C hardness gradientprogressing from a hard core outer surface to a very soft center,whereas the core of golf ball Comp. Ex. 2 has a center Shore C hardnessabove 50 and a much more shallow Shore C hardness gradient from outersurface to center and well below “at least 40”.

In a golf ball of the invention, the solid inner core layer is formedfrom an unfoamed composition selected from thermoplastic compositionsthat can be formulated to provide a very soft, low compression center.Non-limiting examples of suitable inner core layer materials includeRiteflex ®425, Pebax® 2533 SA 01, Pebax® Rnew 25R53 SP 01, Kraton® D0243B, Kraton® D1101 A, Kraton® D1101 B, Kraton® D1101 K, Kraton® D1102 K,Kraton® D1118 B, Estane ® S180A TPU, Estane® S385A TPU, Estane T370ATPU, Estane ® UB400 TPU, Fusbond® 525D, Fusabond® C190, Nucrel ® 9-1,Elvax ® 260, Elvax® 240W, Elvax ® 150, and Elvax® 40W.

Thermoplastic compositions suitable for forming the inner core layerinclude ionomers; non-ionomeric acid polymers, such as E/Y- andE/X/Y-type copolymers, wherein E is an α-olefin (e.g., ethylene), Y is acarboxylic acid such as acrylic, methacrylic, crotonic, maleic, fumaric,or itaconic acid, and X is a softening comonomer such as vinyl esters ofaliphatic carboxylic acids wherein the acid has from 2 to 10 carbons,alkyl ethers wherein the alkyl group has from 1 to 10 carbons, and alkylalkylacrylates such as alkyl methacrylates wherein the alkyl group hasfrom 1 to 10 carbons; polyurethanes, polyureas, andpolyurethane-polyurea hybrids; polyester-based thermoplastic elastomers;polyamides, copolymers of ionomer and polyamide, polyamide-ethers, andpolyamide-esters; ethylene-based homopolymers and copolymers;propylene-based homopolymers and copolymers; triblock copolymers basedon styrene and ethylene/butylene; derivatives thereof that arecompatibilized with at least one grafted or copolymerized functionalgroup; and combinations of any two or more of the above thermoplasticpolymers.

Ionomers, including partially neutralized ionomers and highlyneutralized ionomers (HNPs), and ionomers formed from blends of two ormore partially neutralized ionomers, blends of two or more highlyneutralized ionomers, and blends of one or more partially neutralizedionomers with one or more highly neutralized ionomers, are particularlysuitable for forming the core layers. For purposes of the presentdisclosure, “HNP” refers to an acid copolymer after at least 80% of allacid groups present in the composition are neutralized. Preferredionomers are salts of E/X- and E/X/Y-type acid copolymers, wherein E isan α-olefin (e.g., ethylene), X is a C₃-C₈ α,β-ethylenically unsaturatedcarboxylic acid, and Y is a softening monomer. X is preferably selectedfrom methacrylic acid, acrylic acid, ethacrylic acid, crotonic acid, anditaconic acid. Methacrylic acid and acrylic acid are particularlypreferred. Y is preferably selected from (meth)acrylate andalkyl(meth)acrylates wherein the alkyl groups have from 1 to 8 carbonatoms, including, but not limited to, n-butyl(meth)acrylate,isobutyl(meth)acrylate, methyl(meth)acrylate, and ethyl(meth)acrylate.Particularly preferred E/X/Y-type copolymers are ethylene/(meth) acrylicacid/n-butyl(meth)acrylate, ethylene/(meth) acrylicacid/isobutyl(meth)acrylate, ethylene/(meth)acrylicacid/methyl(meth)acrylate, and ethylene/(meth)acrylicacid/ethyl(meth)acrylate. As used herein, “(meth)acrylic acid” meansmethacrylic acid and/or acrylic acid. Likewise, “(meth) acrylate” meansmethacrylate and/or acrylate. The α-olefin is typically present in theacid copolymer in an amount of 15 wt % or greater, or 25 wt % orgreater, or 40 wt % or greater, or 60 wt % or greater, based on thetotal weight of the acid copolymer. The acid is typically present in theacid copolymer in an amount of 6 wt % or greater, or 9 wt % or greater,or 10 wt % or greater, or 11 wt % or greater, or 15 wt % or greater, or16 wt % or greater, or in an amount within a range having a lower limitof 1 or 4 or 5 or 6 or 8 or 10 or 11 or 12 or 15 wt % and an upper limitof 15 or 16 or 17 or 19 or 20 or 20.5 or 21 or 25 or 30 or 35 or 40 wt%, based on the total weight of the acid copolymer. The optionalsoftening monomer is typically present in the acid copolymer in anamount within a range having a lower limit of 0 or 1 or 3 or 5 or 11 or15 or 20 wt % and an upper limit of 23 or 25 or 30 or 35 or 50 wt %,based on the total weight of the acid copolymer.

The acid copolymer is at least partially neutralized with a cationsource, optionally in the presence of a high molecular weight organicacid, such as those disclosed in U.S. Patent No. 6,756,436, the entiredisclosure of which is hereby incorporated herein by reference. The acidcopolymer can be reacted with the optional high molecular weight organicacid and the cation source simultaneously, or prior to the addition ofthe cation source. Suitable cation sources include, but are not limitedto, metal ion sources, such as compounds of alkali metals, alkalineearth metals, transition metals, and rare earth elements; ammonium saltsand monoamine salts; and combinations thereof. Preferred cation sourcesare compounds of magnesium, sodium, potassium, cesium, calcium, barium,manganese, copper, zinc, lead, tin, aluminum, nickel, chromium, lithium,and rare earth metals.

Suitable ionomers are further disclosed, for example, in U.S. PatentApplication Publication Nos. 2005/0049367, 2005/0148725, 2005/0020741,2004/0220343, and 2003/0130434, and U.S. Pat. Nos. 5,587,430, 5,691,418,5,866,658, 6,100,321, 6,562,906, 6,653,382, 6,756,436, 6,777,472,6,762,246, 6,815,480, 6,894,098, 6,919,393, 6,953,820, 6,994,638,7,375,151, and 7,652,086, the entire disclosures of which are herebyincorporated herein by reference.

Thermoplastic compositions of the present invention optionally includeadditive(s) and/or filler(s) in an amount of 50 wt % or less, or 30 wt %or less, or 20wt % or less, or 15 wt % or less, based on the totalweight of the thermoplastic composition. Suitable additives and fillersinclude, but are not limited to, chemical blowing and foaming agents,optical brighteners, coloring agents, fluorescent agents, whiteningagents, UV absorbers, light stabilizers, defoaming agents, processingaids, antioxidants, stabilizers, softening agents, fragrance components,plasticizers, impact modifiers, TiO₂, acid copolymer wax, surfactants,performance additives (e.g., A-C® performance additives, particularlyA-C® low molecular weight ionomers and copolymers, A-C® oxidizedpolyethylenes, and A-C® ethylene vinyl acetate waxes, commerciallyavailable from Honeywell International Inc.), fatty acid amides (e.g.,ethylene bis-stearamide and ethylene bis-oleamide), fatty acids andsalts thereof (e.g., stearic acid, oleic acid, zinc stearate, magnesiumstearate, zinc oleate, and magnesium oleate), and fillers, such as zincoxide, tin oxide, barium sulfate, zinc sulfate, calcium oxide, calciumcarbonate, zinc carbonate, barium carbonate, tungsten, tungsten carbide,silica, lead silicate, clay, mica, talc, nano-fillers, carbon black,glass flake, milled glass, flock, fibers, and mixtures thereof. Suitableadditives are more fully described in, for example, U.S. PatentApplication Publication No. 2003/0225197, the entire disclosure of whichis hereby incorporated herein by reference. In a particular embodiment,the total amount of additive(s) and filler(s) present in thethermoplastic composition is 20 wt % or less, or 15 wt % or less, or 12wt % or less, or 10 wt % or less, or 9 wt % or less, or 6 wt % or less,or 5 wt % or less, or 4 wt % or less, or 3 wt % or less, or within arange having a lower limit of 0 or 2 or 3 or 5 wt %, based on the totalweight of the thermoplastic composition, and an upper limit of 9 or 10or 12 or 15 or 20 wt %, based on the total weight of the thermoplasticcomposition. In a particular aspect of this embodiment, thethermoplastic composition includes filler(s) selected from carbon black,micro- and nano-scale clays and organoclays, including (e.g., Cloisite®and Nanofil® nanoclays, commercially available from Southern ClayProducts, Inc.; Nanomax® and Nanomer® nanoclays, commercially availablefrom Nanocor, Inc., and Perkalite® nanoclays, commercially availablefrom Akzo Nobel Polymer Chemicals), micro- and nano-scale talcs (e.g.,Luzenac HAR® high aspect ratio talcs, commercially available fromLuzenac America, Inc.), glass (e.g., glass flake, milled glass,microglass, and glass fibers), micro- and nano-scale mica and mica-basedpigments (e.g., Iriodin® pearl luster pigments, commercially availablefrom The Merck Group), and combinations thereof. Particularly suitablecombinations of fillers include, but are not limited to, micro-scalefiller(s) combined with nano-scale filler(s), and organic filler(s) withinorganic filler(s).

Examples of commercially available thermoplastics suitable for formingthe inner core layer include, but are not limited to, ^(Surlyn)® ionomerresins, Hytrel® thermoplastic polyester elastomers, ionomeric materialssold under the trade names DuPont° HPF 1000 and HPF 2000, Nucrel® acidcopolymer resins, Fusabond® metallocene-catalyzed polyethylenes,Fusabond® functionalized ethylene acrylate copolymers, Fusabond®functionalized ethylene vinyl acetate copolymers, Fusabond® anhydridemodified HDPEs, Fusabond® random ethylene copolymers, Fusabond®chemically modified ethylene elastomers, and Fusabond® functionalizedpolypropylenes, all of which are commercially available from E. I. duPont de Nemours and Company; lotek® ionomers, commercially availablefrom ExxonMobil Chemical Company; Amplify° IO ionomers of ethyleneacrylic acid copolymers, commercially available from The Dow ChemicalCompany; Clarix® ionomer resins, commercially available from A. SchulmanInc.; Elastollan® polyurethane-based thermoplastic elastomers,commercially available from BASF; Pebax® thermoplastic polyether andpolyester amides, Lotader® ethylene/acrylic ester/maleic anhydriderandom terpolymers and Lotader® ethylene/ethyl acrylate/maleic anhydriderandom terpolymers, all of which are commercially available from ArkemaInc.; Kraton® linear triblock copolymers based on styrene andethylene/butylene, commercially available from Kraton PerformancePolymers Inc.; and Riteflex® polyester elastomers, commerciallyavailable from Ticona.

The inner and outer core layers of the type set forth in TABLE II areformulated to have different properties and they are formed fromdifferent types of compositions. For example, the inner core layer maybe formed from an ionomer composition and the outer core layer is formedfrom a polybutadiene composition. Thermoset rubber compositions suitablefor forming the outer core layer are those that can be formulated toprovide an outer core surface hardness such that the core has an overallvery high positive hardness gradient of at least 40 Shore C.

For example, the outer core layer core may be made from a compositionincluding at least one thermoset base rubber, such as a polybutadienerubber, cured with at least one peroxide and at least one reactiveco-agent, which can be a metal salt of an unsaturated carboxylic acid,such as acrylic acid or methacrylic acid, a non-metallic coagent, ormixtures thereof. Preferably, a suitable antioxidant is included in thecomposition. An optional soft and fast agent (and sometimes acis-to-trans catalyst), such as an organosulfur or metal-containingorganosulfur compound, can also be included in the core formulation.

The degree of cros slinking of the rubber may be increased by increasingthe amount (phr) of peroxide added. Meanwhile, zinc diacrylate is acoagent commonly used with peroxide to increase the state of cure, totake part in the cross-linking of polybutadiene. A small amount of ZDAand/or ZDMA produces a golf ball core with lower initial velocity andlower compression than a larger amount of coagent. The use of ZDAcoagent may increase velocity and hardness and contribute to a hardfeel. Thus, the amount of peroxide initiator and coagent can be variedto achieve a desired hardness. Antioxidants are compounds that inhibitor prevent the oxidative breakdown of elastomers, and/or inhibit orprevent reactions that are promoted by oxygen radicals.

Other ingredients that are known to those skilled in the art may beused, and are understood to include, but not be limited to,density-adjusting fillers, process aides, plasticizers, blowing orfoaming agents, sulfur accelerators, and/or non-peroxide radicalsources. The base thermoset rubber, which can be blended with otherrubbers and polymers, typically includes a natural or synthetic rubber.A preferred base rubber is 1,4-polybutadiene having a cis structure ofat least 40%, preferably greater than 80%, and more preferably greaterthan 90%. Examples of desirable polybutadiene rubbers include BUNA® CB22and BUNA® CB23, commercially available from LANXESS Corporation; UBEPOL®360L and UBEPOL® 150L and UBEPOL-BR rubbers, commercially available fromUBE Industries, Ltd. of Tokyo, Japan; BUDENE 1208, 1207, commerciallyavailable from Goodyear of Akron, Ohio; and CB BUNA® 1203G1, 1220, and1221, commercially available from LANXESS Corporation; Europrene®NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa;and BR 01, BR 730, BR 735, BR 11, and BR 51, commercially available fromJapan Synthetic Rubber Co., Ltd; and KARBOCHEM® ND40, ND45, and ND60,commercially available from Karbochem.

The base rubber may also comprise high or medium Mooney viscosityrubber, or blends thereof. A “Mooney” unit is a unit used to measure theresistance to flow of raw or unvulcanized rubber. The viscosity in a“Mooney” unit is equal to the torque, measured on an arbitrary scale, ona disk in a vessel that contains rubber at a temperature of 100° C. androtates at two revolutions per minute. The measurement of Mooneyviscosity is defined according to ASTM D-1646.

The Mooney viscosity range is preferably greater than about 40, morepreferably in the range from about 40 to about 80 and more preferably inthe range from about 40 to about 60. Polybutadiene rubber with higherMooney viscosity may also be used, so long as the viscosity of thepolybutadiene does not reach a level where the high viscositypolybutadiene adversely interferes with the manufacturing machinery. Itis contemplated that polybutadiene with viscosity less than 65 Mooneycan be used with the present invention.

In one embodiment of the present invention, golf ball cores made withmid- to high-Mooney viscosity polybutadiene material exhibit increasedresiliency (and, therefore, distance) without increasing the hardness ofthe ball. Such cores are soft, i.e., compression less than about 60 andmore specifically in the range of about 50-55. Cores with compression inthe range of from about 30 about 50 are also within the range of thispreferred embodiment.

Commercial sources of suitable mid- to high-Mooney viscositypolybutadiene include LANXESS CB23 (Nd-catalyzed), which has a Mooneyviscosity of around 50 and is a highly linear polybutadiene. If desired,the polybutadiene can also be mixed with other elastomers known in theart, such as other polybutadiene rubbers, natural rubber, styrenebutadiene rubber, and/or isoprene rubber in order to further modify theproperties of the core. When a mixture of elastomers is used, theamounts of other constituents in the core composition are typicallybased on 100 parts by weight of the total elastomer mixture.

In one preferred embodiment, the base rubber comprises an Nd-catalyzedpolybutadiene, a non-rare earth-catalyzed polybutadiene rubber, orblends thereof. If desired, the polybutadiene can also be mixed withother elastomers known in the art such as natural rubber, polyisoprenerubber and/or styrene-butadiene rubber in order to modify the propertiesof the core. Other suitable base rubbers include thermosetting materialssuch as, ethylene propylene diene monomer rubber, ethylene propylenerubber, butyl rubber, halobutyl rubber, hydrogenated nitrile butadienerubber, nitrile rubber, and silicone rubber.

Thermoplastic elastomers (TPE) may also be used to modify the propertiesof the core layers, or the uncured core layer stock by blending with thebase thermoset rubber. These TPEs include styrenic block copolymers,such as styrene ethylene butadiene styrene, styrene-isoprene-styrene,etc., a metallocene or other single-site catalyzed polyolefin such asethylene-octene, or ethylene-butene, or thermoplastic polyurethanes(TPU), including copolymers. Other suitable TPEs for blending with thethermoset rubbers of the present invention include PEBAX®, which isbelieved to comprise polyether amide copolymers, HYTREL®, which isbelieved to comprise polyether ester copolymers, thermoplastic urethane,and KRATON®, which is believed to comprise styrenic block copolymerselastomers. Any of the TPEs or TPUs above may also contain functionalitysuitable for grafting, including maleic acid or maleic anhydride.

Additional polymers may also optionally be incorporated into the baserubber. Examples include, but are not limited to, thermoset elastomerssuch as core regrind, thermoplastic vulcanizate, copolymeric ionomer,terpolymeric ionomer, polycarbonate, polyamide, copolymeric polyamide,polyesters, polyvinyl alcohols, acrylonitrile-butadiene-styrenecopolymers, polyarylate, polyacrylate, polyphenylene ether,impact-modified polyphenylene ether, high impact polystyrene, diallylphthalate polymer, styrene-acrylonitrile polymer (SAN) (includingolefin-modified SAN and acrylonitrile-styrene-acrylonitrile polymer),styrene-maleic anhydride copolymer, styrenic copolymer, functionalizedstyrenic copolymer, functionalized styrenic terpolymer, styrenicterpolymer, cellulose polymer, liquid crystal polymer, ethylene-vinylacetate copolymers, polyurea, and polysiloxane or anymetallocene-catalyzed polymers of these species.

Suitable polyamides for use as an additional polymeric material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, or decamethylenediamine,1,4-cyclohexanediamine, or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or Ω-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include NYLON 6, NYLON 66, NYLON 610, NYLON 11, NYLON 12,copolymerized NYLON, NYLON MXD6, and NYLON 46.

Suitable peroxide initiating agents include dicumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexane;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne;2,5-dimethyl-2,5-di(benzoylperoxy)hexane;2,2’-bis(t-butylperoxy)-di-iso-propylbenzene;1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide;n-butyl 4,4′-bis(butylperoxy) valerate; di-t-butyl peroxide; or2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl peroxide, t-butylhydroperoxide, α-αbis(t-butylperoxy)diisopropylbenzen,di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl peroxide, di-t-butylperoxide. Preferably, the rubber composition includes from about 0.25 toabout 5.0 parts by weight peroxide per 100 parts by weight rubber (phr),more preferably 0.5 phr to 3 phr, most preferably 0.5 phr to 1.5 phr. Ina most preferred embodiment, the peroxide is present in an amount ofabout 0.8 phr. These ranges of peroxide are given assuming the peroxideis 100% active, without accounting for any carrier that might bepresent. Because many commercially available peroxides are sold alongwith a carrier compound, the actual amount of active peroxide presentmust be calculated. Commercially-available peroxide initiating agentsinclude DICUP™ family of dicumyl peroxides (including DICUP™ R, DICUP™40C and DICUP™ 40KE) available from ARKEMA. Similar initiating agentsare available from AkroChem, Lanxess, Flexsys/Harwick and R. T.Vanderbilt. Another commercially-available and preferred initiatingagent is TRIGONOX™ 265-50B from Akzo Nobel, which is a mixture of1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane anddi(2-t-butylperoxyisopropyl)benzene. TRIGONOX™ peroxides are generallysold on a carrier compound.

Suitable reactive co-agents include, but are not limited to, metal saltsof diacrylates, dimethacrylates, and monomethacrylates suitable for usein this invention include those wherein the metal is zinc, magnesium,calcium, barium, tin, aluminum, lithium, sodium, potassium, iron,zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but thepresent invention is not limited thereto. ZDA provides golf balls with ahigh initial velocity. The ZDA can be of various grades of purity. Forthe purposes of this invention, the lower the quantity of zinc stearatepresent in the ZDA the higher the ZDA purity. ZDA containing less thanabout 10% zinc stearate is preferable. More preferable is ZDA containingabout 4-8% zinc stearate. Suitable, commercially available zincdiacrylates include those from Cray Valley. The preferred concentrationsof ZDA that can be used are about 10 phr to about 40 phr, morepreferably 20 phr to about 35 phr, most preferably 25 phr to about 35phr. In a particularly preferred embodiment, the reactive co-agent ispresent in an amount of about 29 phr to about 31 phr.

Additional preferred co-agents that may be used alone or in combinationwith those mentioned above include, but are not limited to,trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, andthe like. It is understood by those skilled in the art, that in the casewhere these co-agents may be liquids at room temperature, it may beadvantageous to disperse these compounds on a suitable carrier topromote ease of incorporation in the rubber mixture.

Antioxidants are compounds that inhibit or prevent the oxidativebreakdown of elastomers, and/or inhibit or prevent reactions that arepromoted by oxygen radicals. Some exemplary antioxidants that may beused in the present invention include, but are not limited to, quinolinetype antioxidants, amine type antioxidants, and phenolic typeantioxidants. A preferred antioxidant is2,2′-methylene-bis-(4-methyl-6-t-butylphenol) available as VANOX® MBPCfrom R. T. Vanderbilt. Other polyphenolic antioxidants include VANOX® T,VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290. Suitableantioxidants include, but are not limited to, alkylene-bis-alkylsubstituted cresols, such as 4,4′-methylene-bis(2,5-xylenol);4,4′-ethylidene-bis-(6-ethyl-m-cresol); 4,4′-butylidene-bis-(6-t-butyl-m-cresol); 4,4′-decylidene-bis-(6-methyl-m-cresol);4,4′-methylene-bis-(2-amyl-m-cresol);4,4′-propylidene-bis-(5-hexyl-m-cresol);3,3′-decylidene-bis-(5-ethyl-p-cresol);2,2′-butylidene-bis-(3-n-hexyl-p-cresol);4,4′-(2-butylidene)-bis-(6-t-butyl-m-cresol);3,3′-4(decylidene)-bis-(5-ethyl-p-cresol);(2,5-dimethyl-4-hydroxyphenyl) (2-hydroxy-3,5-dimethylphenyl)methane;(2-methyl-4-hydroxy-5-ethylphenyl)(2-ethyl-3-hydroxy-5-methylphenyl)methane;(3-methyl-5-hydroxy-6-t-butylphenyl)(2-hydroxy-4-methyl-5-decylphenyl)-n-butyl methane;(2-hydroxy-4-ethyl-5-methylphenyl)(2-decyl-3-hydroxy-4-methylphenyl)butylamylmethane;(3-ethyl-4-methyl-5-hydroxyphenyl)-(2,3-dimethyl-3-hydroxy-phenyl)nonylmethane;(3-methyl-2-hydroxy-6-ethylphenyl)-(2-isopropyl-3-hydroxy-5-methyl-phenyl)cyclohexylmethane;(2-methyl-4-hydroxy-5-methylphenyl)(2-hydroxy-3-methyl-5-ethylphenyl)dicyclohexyl methane; and the like.

Other suitable antioxidants include, but are not limited to, substitutedphenols, such as 2-tert-butyl-4-methoxyphenol;3-tert-butyl-4-methoxyphenol; 3-tert-octyl-4-methoxyphenol;2-methyl-4-methoxyphenol; 2-stearyl-4-n-butoxyphenol;3-t-butyl-4-stearyloxyphenol; 3-lauryl-4-ethoxyphenol;2,5-di-t-butyl-4-methoxyphenol; 2-methyl-4-methoxyphenol;241-methycyclohexyl)-4-methoxyphenol; 2-t-butyl-4-dodecyloxyphenol;2-(1-methylbenzyl)-4-methoxyphenol; 2-t-octyl-4-methoxyphenol; methylgallate; n-propyl gallate; n-butyl gallate; lauryl gallate; myristylgallate; stearyl gallate; 2,4,5-trihydroxyacetophenone;2,4,5-trihydroxy-n-butyrophenone; 2,4,5-trihydroxystearophenone;2,6-ditert-butyl-4-methylphenol; 2,6-ditert-octyl-4-methylphenol;2,6-ditert-butyl-4-stearylphenol; 2-methyl-4-methyl-6-tert-butylphenol;2,6-distearyl-4-methylphenol; 2,6-dilauryl-4-methylphenol;2,6-di(n-octyl)-4-methylphenol; 2,6-di(n-hexadecyl)-4-methylphenol;2,6-di(1-methylundecyl)-4-methylphenol;2,6-di(1-methylheptadecyl)-4-methylphenol;2,6-di(trimethylhexyl)-4-methylphenol;2,6-di(1,1,3,3-tetramethyloctyl)-4-methylphenol; 2-n-dodecyl-6-tertbutyl-4-methylphenol; 2-n-dodecyl-6-(1-methylundecyl)-4-methylphenol;2-n-dodecyl-6-(1,1,3,3-tetramethyloctyl)-4-methylphenol;2-n-dodecyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-n-octyl-4-methylphenol;2-methyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-(1-methylheptadecyl)-4-methylphenol;2,6-di(1-methylbenzyl)-4-methylphenol;2,6-di(1-methylcyclohexyl)-4-methylphenol;2,6-(1-methylcyclohexyl)-4-methylphenol;2-(1-methylbenzyl)-4-methylphenol; and related substituted phenols.

More suitable antioxidants include, but are not limited to, alkylenebisphenols, such as 4,4′-butylidene bis(3-methyl-6-t-butyl phenol);2,2-butylidene bis (4,6-dimethyl phenol); 2,2′-butylidenebis(4-methyl-6-t-butyl phenol); 2,2′-butylidene bis(4-t-butyl-6-methylphenol); 2,2′-ethylidene bis(4-methyl-6-t-butylphenol); 2,2′-methylenebis(4,6-dimethyl phenol); 2,2′-methylene bis(4-methyl-6-t-butyl phenol);2,2′-methylene bis(4-ethyl-6-t-butyl phenol); 4,4′-methylenebis(2,6-di-t-butyl phenol); 4,4′-methylene bis(2-methyl-6-t-butylphenol); 4,4′-methylene bis(2,6-dimethyl phenol); 2,2′-methylenebis(4-t-butyl-6-phenyl phenol);2,2′-dihydroxy-3,3′,5,5′-tetramethylstilbene; 2,2′-isopropylidenebis(4-methyl-6-t-butyl phenol); ethylene bis (beta-naphthol);1,5-dihydroxy naphthalene; 2,2′-ethylene bis (4-methyl-6-propyl phenol);4,4′-methylene bis(2-propyl-6-t-butyl phenol); 4,4′-ethylene bis(2-methyl-6-propyl phenol); 2,2′-methylene bis(5-methyl-6-t-butylphenol); and 4,4′-butylidene bis(6-t-butyl-3-methyl phenol);

Suitable antioxidants further include, but are not limited to, alkylenetrisphenols, such as 2,6-bis (2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methyl phenol; 2,6-bis (2′-hydroxy-3′-t-ethyl-5′-butylbenzyl)-4-methyl phenol; and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-propylbenzyl)-4-methyl phenol.

The antioxidant is typically present in an amount of about 0.1 phr toabout 5 phr, preferably from about 0.1 phr to about 2 phr, morepreferably about 0.1 phr to about 1 phr. In a particularly preferredembodiment, the antioxidant is present in an amount of about 0.4 phr. Inan alternative embodiment, the antioxidant should be present in anamount to ensure that the hardness gradient of the inventive cores isnegative. Preferably, about 0.2 phr to about 1 phr antioxidant is addedto the core layer (inner core or outer core layer) formulation, morepreferably, about 0.3 to about 0.8 phr, and most preferably 0.4 to about0.7 phr. Preferably, about 0.25 phr to about 1.5 phr of peroxide ascalculated at 100% active can be added to the core formulation, morepreferably about 0.5 phr to about 1.2 phr, and most preferably about 0.7phr to about 1.0 phr. The ZDA amount can be varied to suit the desiredcompression, spin and feel of the resulting golf ball. The cure regimecan have a temperature range between from about 290° F. to about 360°F., or from about 290° F. to about 335° F., or from about 300° F. toabout 325° F., or from about 330° F. to about 355° F., and the stock isheld at that temperature for at least about 10 minutes to about 30minutes.

The thermoset rubber composition in a core of the golf ball of thepresent invention may also include an optional soft and fast agent. Asused herein, “soft and fast agent” means any compound or a blend thereofthat that is capable of making a core 1) be softer (lower compression)at constant COR or 2) have a higher COR at equal compression, or anycombination thereof, when compared to a core equivalently preparedwithout a soft and fast agent. Preferably, the composition of thepresent invention contains from about 0.05 phr to about 10.0 phr softand fast agent. In one embodiment, the soft and fast agent is present inan amount of about 0.05 phr to about 3.0 phr, preferably about 0.05 phrto about 2.0 phr, more preferably about 0.05 phr to about 1.0 phr. Inanother embodiment, the soft and fast agent is present in an amount ofabout 2.0 phr to about 5.0 phr, preferably about 2.35 phr to about 4.0phr, and more preferably about 2.35 phr to about 3.0 phr. In analternative high concentration embodiment, the soft and fast agent ispresent in an amount of about 5.0 phr to about 10.0 phr, more preferablyabout 6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about8.0 phr. In a most preferred embodiment, the soft and fast agent ispresent in an amount of about 2.6 phr.

Suitable soft and fast agents include, but are not limited to,organosulfur or metal-containing organosulfur compounds, an organicsulfur compound, including mono, di, and polysulfides, a thiol, ormercapto compound, an inorganic sulfide compound, a Group VIA compound,or mixtures thereof. The soft and fast agent component may also be ablend of an organosulfur compound and an inorganic sulfide compound.

Suitable soft and fast agents of the present invention include, but arenot limited to those having the following general formula:

where R₁-R₅ can be C₁-C₈ alkyl groups; halogen groups; thiol groups(—SH), carboxylated groups; sulfonated groups; and hydrogen; in anyorder; and also pentafluorothiophenol; 2-fluorothiophenol;3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol;2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their zinc salts. Preferably, thehalogenated thiophenol compound is pentachlorothiophenol, which iscommercially available in neat form or under the tradename STRUKTOL®, aclay-based carrier containing the sulfur compound pentachlorothiophenolloaded at 45 percent (correlating to 2.4 parts PCTP). STRUKTOL® iscommercially available from Struktol Company of America of Stow, Ohio.PCTP is commercially available in neat form from eChinachem of SanFrancisco, Calif. and in the salt form from eChinachem of San Francisco,Calif. Most preferably, the halogenated thiophenol compound is the zincsalt of pentachlorothiophenol, which is commercially available fromeChinachem of San Francisco, Calif.

As used herein when referring to the invention, the term “organosulfurcompound(s)” refers to any compound containing carbon, hydrogen, andsulfur, where the sulfur is directly bonded to at least 1 carbon. Asused herein, the term “sulfur compound” means a compound that iselemental sulfur, polymeric sulfur, or a combination thereof. It shouldbe further understood that the term “elemental sulfur” refers to thering structure of S₈ and that “polymeric sulfur” is a structureincluding at least one additional sulfur relative to elemental sulfur.

Additional suitable examples of soft and fast agents (that are alsobelieved to be cis-to-trans catalysts) include, but are not limited to,4,4′-diphenyl disulfide; 4,4′-ditolyl disulfide; 2,2′-benzamido diphenyldisulfide; bis(2-aminophenyl)disulfide; bis(4-aminophenyl)disulfide;bis(3-aminophenyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide;2,2′-bis(3-aminonaphthyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide;2,2′-bis(5-aminonaphthyl)disulfide; 2,2′-bis(6-aminonaphthyl)disulfide;2,2′-bis(7-aminonaphthyl)disulfide; 2,2′-bis(8-aminonaphthyl)disulfide;1,1′-bis(2-aminonaphthyl)disulfide; 1,1′-bis(3-aminonaphthyl)disulfide;1,1′-bis(3-aminonaphthyl)disulfide; 1,1′-bis(4-aminonaphthyl)disulfide;1,1′-bis(5-aminonaphthyl) disulfide; 1,1′-bis(6-aminonaphthyl)disulfide;1,1′-bis(7-aminonaphthyl)disulfide; 1,1′-bis(8-aminonaphthyl)disulfide;1,2′-diamino-1,2′-dithiodinaphthalene;2,3′-diamino-1,2′-dithiodinaphthalene; bis(4-chlorophenyl)disulfide;bis(2-chlorophenyl)disulfide; bis(3-chlorophenyl)disulfide;bis(4-bromophenyl)disulfide; bis(2-bromophenyl)disulfide;bis(3-bromophenyl)disulfide; bis(4-fluorophenyl)disulfide;bis(4-iodophenyl)disulfide; bis(2,5-dichlorophenyl)disulfide;bis(3,5-dichlorophenyl)disulfide; bis (2,4-dichlorophenyl)disulfide;bis(2,6-dichlorophenyl)disulfide; bis(2,5-dibromophenyl)disulfide;bis(3,5-dibromophenyl)disulfide; bis(2-chloro-5-bromophenyl)disulfide;bis(2,4,6-trichlorophenyl)disulfide;bis(2,3,4,5,6-pentachlorophenyl)disulfide; bis(4-cyanophenyl)disulfide;bis(2-cyanophenyl)disulfide; bis(4-nitrophenyl)disulfide;bis(2-nitrophenyl)disulfide; 2,2′-dithiobenzoic acid ethylester;2,2′-dithiobenzoic acid methylester; 2,2′-dithiobenzoic acid;4,4′-dithiobenzoic acid ethylester; bis(4-acetylphenyl)disulfide;bis(2-acetylphenyl)disulfide; bis(4-formylphenyl)disulfide;bis(4-carbamoylphenyl)disulfide; 1,1′-dinaphthyl disulfide;2,2′-dinaphthyl disulfide; 1,2′-dinaphthyl disulfide;2,2′-bis(1-chlorodinaphthyl)disulfide;2,2′-bis(1-bromonaphthyl)disulfide; 1,1′-bis(2-chloronaphthyl)disulfide;2,2′-bis(1-cyanonaphthyl)disulfide; 2,2′-bis(1-acetylnaphthyl)disulfide;and the like; or a mixture thereof. Preferred organosulfur componentsinclude 4,4′-diphenyl disulfide, 4,4′-ditolyl disulfide, or2,2′-benzamido diphenyl disulfide, or a mixture thereof. A morepreferred organosulfur component includes 4,4′-ditolyl disulfide. Inanother embodiment, metal-containing organosulfur components can be usedaccording to the invention. Suitable metal-containing organosulfurcomponents include, but are not limited to, cadmium, copper, lead, andtellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof.

Suitable substituted or unsubstituted aromatic organic components thatdo not include sulfur or a metal include, but are not limited to,4,4′-diphenyl acetylene, azobenzene, or a mixture thereof. The aromaticorganic group preferably ranges in size from C₆ to C₂₀, and morepreferably from C₆ to C₁₀. Suitable inorganic sulfide componentsinclude, but are not limited to titanium sulfide, manganese sulfide, andsulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper,selenium, yttrium, zinc, tin, and bismuth.

A substituted or unsubstituted aromatic organic compound is alsosuitable as a soft and fast agent. Suitable substituted or unsubstitutedaromatic organic components include, but are not limited to, componentshaving the formula (R₁)_(x)-R₃-M-R₄-(R₂)_(y), wherein R₁ and R₂ are eachhydrogen or a substituted or unsubstituted C₁₋₂₀ linear, branched, orcyclic alkyl, alkoxy, or alkylthio group, or a single, multiple, orfused ring C₆ to C₂₄ aromatic group; x and y are each an integer from 0to 5; R₃ and R₄ are each selected from a single, multiple, or fused ringC₆ to C₂₄ aromatic group; and M includes an azo group or a metalcomponent. R₃ and R₄ are each preferably selected from a C₆ to C₁₀aromatic group, more preferably selected from phenyl, benzyl, naphthyl,benzamido, and benzothiazyl. R₁ and R₂ are each preferably selected froma substituted or unsubstituted C₁₋₁₀ linear, branched, or cyclic alkyl,alkoxy, or alkylthio group or a C₆ to C₁₀ aromatic group. When R₁, R₂,R₃, or R₄, are substituted, the substitution may include one or more ofthe following substituent groups: hydroxy and metal salts thereof;mercapto and metal salts thereof; halogen; amino, nitro, cyano, andamido; carboxyl including esters, acids, and metal salts thereof; silyl;acrylates and metal salts thereof; sulfonyl or sulfonamide; andphosphates and phosphites. When M is a metal component, it may be anysuitable elemental metal available to those of ordinary skill in theart. Typically, the metal will be a transition metal, althoughpreferably it is tellurium or selenium. In one embodiment, the aromaticorganic compound is substantially free of metal, while in anotherembodiment the aromatic organic compound is completely free of metal.

The soft and fast agent can also include a Group VIA component.Elemental sulfur and polymeric sulfur are commercially available fromElastochem, Inc. of Chardon, Ohio. Exemplary sulfur catalyst compoundsinclude PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymeric sulfur,each of which is available from Elastochem, Inc. An exemplary telluriumcatalyst under the tradename TELLOY® and an exemplary selenium catalystunder the tradename VANDEX® are each commercially available from RTVanderbilt.

Fillers may also be added to the thermoset rubber composition of thecore to adjust the density of the composition, up or down. Typically,fillers include materials such as tungsten, zinc oxide, barium sulfate,silica, calcium carbonate, zinc carbonate, metals, metal oxides andsalts, regrind (recycled core material typically ground to about 30 meshparticle), high-Mooney-viscosity rubber regrind, trans-regrind corematerial (recycled core material containing high trans- isomer ofpolybutadiene), and the like. When trans-regrind is present, the amountof trans- isomer is preferably between about 10% and about 60%. In apreferred embodiment of the invention, the core comprises polybutadienehaving a cis- isomer content of greater than about 95% and trans-regrindcore material (already vulcanized) as a filler. Any particle sizetrans-regrind core material is sufficient, but is preferably less thanabout 125 pm.

Fillers added to one or more portions of the golf ball typically includeprocessing aids or compounds to affect rheological and mixingproperties, density-modifying fillers, tear strength, or reinforcementfillers, and the like. The fillers are generally inorganic, and suitablefillers include numerous metals or metal oxides, such as zinc oxide andtin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate,barium carbonate, clay, tungsten, tungsten carbide, an array of silicas,and mixtures thereof. Fillers may also include various foaming agents orblowing agents which may be readily selected by one of ordinary skill inthe art. Fillers may include polymeric, ceramic, metal, and glassmicrospheres may be solid or hollow, and filled or unfilled. Fillers aretypically also added to one or more portions of the golf ball to modifythe density thereof to conform to uniform golf ball standards. Fillersmay also be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

Materials such as tungsten, zinc oxide, barium sulfate, silica, calciumcarbonate, zinc carbonate, metals, metal oxides and salts, and regrind(recycled core material typically ground to about 30 mesh particle) arealso suitable fillers.

The polybutadiene and/or any other base rubber or elastomer system mayalso be foamed, or filled with hollow microspheres or with expandablemicrospheres which expand at a set temperature during the curing processto any low specific gravity level. Other ingredients such as sulfuraccelerators, e.g., tetramethylthiuram di, tri, or tetrasulfide, and/ormetal-containing organosulfur components may also be used according tothe invention. Suitable metal-containing organosulfur acceleratorsinclude, but are not limited to, cadmium, copper, lead, and telluriumanalogs of diethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof. Other ingredients such asprocessing aids e.g., fatty acids and/or their metal salts, processingoils, dyes and pigments, as well as other additives known to one skilledin the art may also be used in the present invention in amountssufficient to achieve the purpose for which they are typically used.

Without being bound by theory, it is believed that the percentage ofdouble bonds in the trans configuration may be manipulated throughout acore containing at least one main-chain unsaturated rubber (i.e.,polybutadiene), plastic, or elastomer resulting in a trans gradient. Thetrans gradient may be influenced (up or down) by changing the type andamount of cis-to-trans catalyst (or soft-and-fast agent), the type andamount of peroxide, and the type and amount of coagent in theformulation. For example, a formulation containing about 0.25 phr ZnPCTPmay have a trans gradient of about 5% across the core whereas aformulation containing about 2 phr ZnPCTP may have a trans gradient ofabout 10%, or higher. The trans gradient may also be manipulated throughthe cure times and temperatures. It is believed that lower temperaturesand shorter cure times yield lower trans gradients, although acombination of many of these factors may yield gradients of differingand/or opposite directions from that resulting from use of a singlefactor.

In general, higher and/or faster cure rates tend to yield higher levelsof trans content, as do higher concentrations of peroxides,soft-and-fast agents, and, to some extent, ZDA concentration. Even thetype of rubber may have an effect on trans levels, with those catalyzedby rare-earth metals, such as Nd, being able to form higher levels oftrans polybutadiene compared to those rubbers formed from Group VIIImetals, such as Co, Ni, and Li.

Meanwhile, in a different embodiment, the thermoplastic inner and outercore layers of a golf ball of the invention of the type set forth inTABLE V are also formulated to have properties that differ as disclosedherein. Non-limiting examples of suitable thermoplastic materials for aninner core layer and outer core layer of a golf ball of the invention inthis embodiment appear in TABLE V and elsewhere herein.

Two further different constructions are illustrated in prophetic golfballs Ex. 9, Ex. 10 and Ex. 11 below and compared with one conventionalprophetic golf ball Comp. Ex. 3. Each of golf balls Ex. 9, Ex. 10 andEx. 11 incorporate an inner core layer formed from a transparent orplasticized polyamide composition and an outer core layer formed from atleast one of a thermoset rubber composition and a thermoplasticcomposition, as follows.

Prophetic inventive golf balls Ex. 9, Ex. 10 and Ex. 11 and comparativeprophetic golf ball Comp. Ex. 3 each comprise a core, a cover, and anintermediate layer disposed between the core and the cover.Additionally, every core is a dual core comprising an inner core layersurrounded by an outer core layer.

The inner core layers of inventive prophetic golf balls Ex. 9, Ex. 10and Ex. 11 are each formed from a different transparent or plasticizedpolyamide composition as formulated in TABLE VI:

TABLE VI INNER CORE LAYER MATERIALS (P_(t/p)) Ingredients Ex. 9 Ex. 10Ex. 11 (Phr) P_(t/p)(1) P_(t/p)(2) P_(t/p)(3) Pebax ®2533 100 90 *Pebax ®3533SA * * 90 Jeffsol Propylene * 10 10 Carbonate ²⁷Pebax ®2533is a polyether block amide (PEBA) available from ARKEMA. 28Pebax ®3533SAis a polyether block amide (PEBA) available from ARKEMA.²⁹Jeffsol ®Propylene Carbonate is available from HUNTSMAN.

As shown in TABLE VI, P_(t/) _(p)(1), P_(t/) _(p)(2), and P_(t)/_(p)(3)differ in at least one of selection of polyether block amide anduse/non-use of plasticizer.

In turn, the outer core layers of golf balls Ex. 9, Ex. 10 and Ex. 11are each formed from a different thermoset rubber composition 1 or 2 asformulated in TABLE VII:

TABLE VII THERMOSET OUTER CORE MATERIALS INGREDIENTS Core Core Core(Phr) Formulation 1 Formulation 2 formulation 3 Polybutadiene 100 100100 Zinc Oxide 5 5 5 Zinc diacrylate 35 38 31 (ZDA) Perkadox ® BC²⁹ 0.50.5 * Trigonox ® 265³⁰ * * 1 Antioxidant * * 0.4 ZnPCTP 0.5 0.5 0.5³⁰Perkadox ® BC is an initiating agent (Dicumyl peroxide) available fromAkzo Nobel. ³¹Trigonox ®265 is an initiating agent available from AkzoNobel.

Meanwhile, in comparative golf ball Comp. Ex. 3, both the inner corelayer and outer core layer are formed from conventional thermosetrubber-based compositions 3 and 1, respectively of TABLE VII above. Asshown in TABLE VII, core formulations 1, 2 and 3 differ from each otherby at least one of the amount of peroxide, the amount of zincdiacrylate, and presence/absence of an antioxidant.

TABLE VIII below incorporates the details of TABLE VI and TABLE VIItherein and further specifies the construction and certain additionalproperties for each of golf balls Ex. 9, Ex. 10, Ex. 11, and Comp. Ex.3:

TABLE VIII Golf Ball EXAMPLES Construction Comp. & Properties Ex. 9 Ex.10 Ex. 11 Ex. 3 Inner Core P_(t/p)(1) P_(t/p) (2) P_(t/p) (3) CoreMaterial Formulation  3³¹   Inner Core 0.75 0.50 0.75  1.00 Diameter(in.) Center 43.4 34.7 47.6 71.0  Hardness (Shore C) Outer Core CoreCore Core Core Material Formulation Formulation Formulation Formulation2 2 1 1   Outer Core 0.400 0.525 0.400  0.275 Thickness (in.) Outer Core87.9 89.3 88.2 87.5  Surf. Hardness (Shore C) Dual Core 81 73 86 88  Compression Intermediate Surlyn ® Surlyn ® Surlyn ® Surlyn ® LayerMaterial 7940/8940³² 7940/8940 7940/8940 7940/8940 Intermediate 0.0350.035 0.035  0.035 Layer Thickness (in.) Intermediate 68.9 69.1 71.469.3  Layer Hardness (Shore D) Cover Material MDI³³/ MDI MDI MDIPTMEG³⁴/ PTMEG PTMEG PTMEG E-300³⁵ E-300 E-300 E-300 Cover 0.030 0.0300.030  0.030 Thickness (in.) Cover 81.5 82.8 83.1 82.1  Hardness (ShoreC) Ball 90 82 101 99   Compression ³²Core Formulations 1, 2 & 3 hereinas set forth in TABLE VII above. ³³Surlyn ®7940 (Li) and Surlyn ®8940(Na), are medium acid, monovalent and medium flow ionomers. ³⁴Methylenediphenyl diisocyanate. ³⁵Polytetramethylene ether glycol. ³⁶Ethacure300, dimethylthiotoluene diamine, sold by Albemarle.

Referring to golf balls Ex. 9, Ex. 10 and Ex. 11 of TABLE VIII, eachdual core comprises a very soft, low compression inner core layersurrounded by a hard higher compression outer core layer. Additionally,each inner core layer has a diameter of less than 1.10 inches, is formedfrom a transparent or plasticized polyamide composition, and has acenter Shore C hardness of 50 or less.

Meanwhile, each outer core layer has a thickness of 0.200 inches orgreater, is formed from a thermosetting rubber composition, and has anouter surface Shore C hardness of 70 or greater. Finally, in each of thedual cores of golf balls Ex. 9, Ex. 10, and Ex. 11, the outer core layerhas an outer surface hardness that is at least 40 Shore C points greaterthan the center hardness of the inner core layer.

Specifically referring to golf ball Ex. 9, the transparent orplasticized polyamide composition inner core layer has a diameter of0.75 in., and has a center Shore C hardness of 43.4. The thermosetrubber outer core layer meanwhile has a thickness of 0.400 in., isformed from core formulation 1, and has an outer surface Shore Chardness of 87.9. The outer surface hardness of the outer core layer ofgolf ball Ex. 9 is therefore “at least 40 Shore C points greater thanthe center hardness of the inner core layer” (namely 44.5 Shore C pointsgreater than the center hardness).

Several property differences may be noted between golf balls Ex. 10 andEx. 11 compared with golf ball Ex. 9, respectively: inner core layercenter Shore C hardnesses (34.7 and 47.6 versus 43.4); outer core layersurface Shore C hardnesses (89.3 and 88.2 versus 87.9); dual corecompressions (73 and 86 versus 81); intermediate layer Shore Dhardnesses (69.1 and 71.4 versus 68.9); cover layer surface shore Chardness (82.8 and 83.1 versus 81.5); and golf ball compression (82 and101 versus 90).

Nevertheless, golf ball Ex. 10 has an outer core layer outer surfacehardness that is greater than the center hardness of the inner corelayer by 54.6 Shore C hardness points (89.3-34.7), well above “at least40 Shore C points greater” of one embodiment of a golf ball of theinvention. Similarly, golf ball Ex. 11 has an outer core layer outersurface hardness that is greater than the center hardness of the innercore layer by 40.6 Shore C hardness points (88.2-47.6), also above “atleast 40 Shore C points greater” of one embodiment of a golf ball of theinvention.

Property differences between golf balls Ex. 9, Ex. 10 and Ex. 11 may beattributed to the outer core layer formulation differences between coreformulation 1 and core formulation 2 as well as to the above-identifiedinner core formulation differences.

Comparative golf ball Comp. Ex. 3, unlike golf balls Ex. 9, Ex. 10, andEx. 11, incorporates conventional thermoset rubber-based compositions inboth the inner core layer and an outer core layer. The inner core layerof Comp. Ex. 3 is formed from a conventional thermoset rubber-basedcomposition having a center Shore C hardness well above 50 (namely 71).Meanwhile, the outer core layer of Comp. Ex. 3 has an outer surfaceShore C hardness that is not “at least 40 Shore C points greater thanthe center hardness of the inner core layer” but rather, well belowthat, namely only 16.5 Shore C points greater.

Accordingly, each of golf balls Ex. 9, Ex. 10 and Ex. 11 incorporates acore having a steep positive Shore C hardness gradient progressing froma hard core outer surface to a very soft center, whereas the core ofgolf ball Comp. Ex. 3 has a center Shore C hardness above 50 and a muchmore shallow Shore C hardness gradient from outer surface to center andwell below “at least 40”. It is envisioned that an inner core of a golfball of the invention may incorporate a transparent or plasticizedpolyamide composition or a combination thereof.

Prophetic golf balls Ex. 9, Ex. 10 and Ex. 11 above demonstrate examplesof inventive golf balls incorporating Pebax ®2533 and Pebax ®35335A inthe inner core layer. In different constructions, an outer core layermay also be formulated to comprise a transparent or plasticizedpolyamide, albeit quite differently.

For example, in several different constructions, a transparent orplasticized polyamide compositon may be formulated as an outer corelayer material as follows. Several such embodiments are illustrated inprophetic golf balls Ex. 5A, Ex. 6A, Ex. 7A, and Ex. 8A and comparedwith one conventional prophetic golf ball Comp. Ex. 2A herein below inTABLES IX:

TABLE IX Golf Ball Construction EXAMPLES & Properties Ex. 5A Ex. 6A Ex.7A Ex. 8A Comp. Ex. 2A Inner Core Layer Elvax ® Nucrel ® Kraton ®Riteflex ® Core Material  150³⁷    9-1³⁸ D0243 B³⁹  425⁴⁰    Formulat.2⁴¹ Inner Core Layer  0.75 0.50 0.75  0.50 1.00 Diam.(in.) CenterHardness 27.1  48.1 36.4 42.8  71.0 (Shore C) Outer Core LayerGrilamid ® Rilsan ® Pebax ® Trogamid ® Core Material TR90⁴² Clear Clear400⁴⁴ T5000⁴⁵ Formulat. 1⁴¹ G350⁴³ Outer Core Layer  0.400 0.525 0.400 0.525 0.275 Thickness (in.) Outer Core Surf. 82.7  79.6 62.3 87.0  60.1Hardness (Shore D) Intermediate Surlyn ® Surlyn ® Surlyn ® Surlyn ®Surlyn ® Layer Material 7940/8940⁴⁶ 7940/8940 7940/8940 7940/89407940/8940 Intermediate  0.035 0.035 0.035  0.035 0.035 Layer Thickness(in.) Intermediate 69.7  69.2 68.8 70.7  69.3 Layer Hardness (Shore D)Cover Material MDI⁴⁷/ MDI/ MDI/ MDI/ MDI/ PTMEG⁴⁸/ PTMEG/ PTMEG/ PTMEG/PTMEG/ E-300⁴⁹ E-300 E-300 E-300 E-300 Cover Thickness  0.030 0.0300.030  0.030 0.030 (in.) Cover Hardness 83.1  83.4 82.7 84.1  82.1(Shore C) ³⁷Elvax ®150 is an ethylene-vinyl acetate copolymer resin(EVA) available from E. I. du Pont de Nemours and Company, Inc.³⁸Nucrel ®9-1 is an olefin-unsaturated carboxylic acid ester terpolymeravailable from E. I. du Pont de Nemours and Company, Inc. ³⁹Kraton ®D0243 B is a diblock copolymer based on styrene and butadiene with apolystyrene content of 33% (styrene block copolymer) available fromKraton Polymers. ⁴⁰Riteflex ®425 is a thermoplastic polyester elastomeravailable from Ticona. ⁴¹Core Formulations 1&2 as set forth in TABLE Iabove. ⁴²Grilamid ® TR90 is a transparent polyamide from EMS-GRIVORY⁴³Rilsan ®Clear G350 is a transparent polyamide from ARKEMA TechnicalPolymers ⁴⁴Pebax ® Clear 400 is a transparent polyamide from ARKEMATechnical Polymers ⁴⁵Trogamid ® T5000 is a transparent polyamide fromEVONIK Industries. ⁴⁶Surlyn ®7940 (Li) and Surlyn ®8940 (Na), are mediumacid, monovalent and medium flow ionomers. ⁴⁷Methylene diphenyldiisocyanate. ⁴⁸Polytetramethylene ether glycol. ⁴⁹Ethacure 300,dimethylthiotoluene diamine, sold by Albemarle.

Referring to golf balls Ex. 5A, Ex. 6A, Ex. 7A, and Ex. 8A of TABLE IX,each dual core comprises a very soft inner core layer surrounded by amuch harder outer core layer. Each inner core layer has a diameter ofless than 1.10 inches, is formed from an unfoamed thermoplasticcomposition, and has a center Shore C hardness of 50 or less. Meanwhile,each outer core layer has a thickness of 0.200 inches or greater, isformed from a second thermoplastic composition comprising a transparentor plasticized polyamide, and has an outer surface Shore D hardness of55 or greater. Finally, in each of the dual cores of golf balls Ex. 5A,Ex. 6A, Ex. 7A, and Ex. 8A, the Shore D hardness of the outer surface,plus 30, is greater than the center Shore C hardness by at least 40.

Specifically referring to golf ball Ex. 5A, the EVA inner core layer hasa diameter of 0.75 in., and has a center Shore C hardness of 27.1, whichis less than 50. The outer core layer meanwhile has a thickness of 0.400in., is formed from Grilamid TR90, and has an outer surface Shore Dhardness of 82.7. The Shore D hardness of the outer surface, plus 30, istherefore greater than the center Shore C hardness by at least 40(namely ((82.7+30)-27.1)≧40).

In golf ball Ex. 6A, the inner core layer is formed from anolefin-unsaturated carboxylic acid ester terpolymer, has a diameter of0.50 in., and has a center Shore C hardness of 48.1, which is less than50. The outer core layer meanwhile has a thickness of 0.525 in., isformed from Rilsan Clear G350, and has an outer surface Shore D hardnessof 79.6. The Shore D hardness of the outer surface, plus 30, istherefore greater than the center Shore C hardness by at least 40(namely 479.6+30)-48.0≧40).

Golf ball Ex. 7A has an inner core layer that is formed from a styreneblock copolymer, has a diameter of 0.75 in., and has a center Shore Chardness of 42.8, which is less than 50. The outer core layer meanwhilehas a thickness of 0.400 in., is formed from Pebax Clear 400, and has anouter surface Shore D hardness of 62.3. The Shore D hardness of theouter surface, plus 30, is therefore greater than the center Shore Chardness by at least 40 (namely((62.3+30)-36.4)>40).

Finally, in golf ball Ex. 8A, the inner core layer is formed from athermoplastic polyester elastomer, has a diameter of 0.50 in., and has acenter Shore C hardness of 42.8, which is less than 50. The outer corelayer meanwhile has a thickness of 0.525 in., is formed from Trogamid®T5000, and has an outer surface Shore D hardness of 87.0. The Shore Dhardness of the outer surface, plus 30, is therefore greater than thecenter Shore C hardness by at least 40 (namely ((87.0+30)-42.8)>40,respectively).

In contrast to golf balls Ex. 5A, Ex. 6A, Ex. 7A, and Ex. 8A,comparative golf ball Comp. Ex. 2A incorporates an inner core layer andan outer core layer that are formed from conventional thermosetrubber-based compositions. The inner core layer of Comp. Ex. 2A has adiameter of 1.0 in. and the outer core layer has a thickness of 0.275in., but the center Shore C hardness well above 50 (namely 71).Meanwhile, the outer core layer of Comp. Ex. 2A has an outer surfaceShore D hardness of 60.1, which plus 30, is greater than the centerShore C hardness by only 19.1, well below “at least 40” of golf balls ofthe invention.

Accordingly, each of golf balls Ex. 5A, Ex. 6A, Ex. 7A, and Ex. 8Aincorporates a core having a steep positive hardness gradientprogressing from a hard core outer surface to a very soft center,whereas the core of golf ball Comp. Ex. 2A has a center Shore C hardnessabove 50 and an outer surface Shore D hardness, plus 30, that is notgreater than the center Shore C hardness by “at least 40”. Golf balls ofthe invention incorporating cores such as depicted in golf balls Ex. 5A,Ex. 6A, Ex. 7A, and Ex. 8A produce a desired spin profile of reducedspin off the driver meanwhile maintaining moderate spin off wedges andirons.

Embodiments are also envisioned wherein golf balls Ex. 5A, Ex. 6A, Ex.7A, and Ex. 8A further include and intermediate core layer between innercore layer TP₁ and outer core layer TP₂. In such an embodiment, theintermediate core layers of golf balls Ex. 5A, Ex. 6A, Ex. 7A, and Ex.8A may be formulated as set forth in TABLE X below, namely the sameformulations as used for the outer core layers of golf balls Ex. 5, Ex.6, Ex. 7, and Ex. 8 of TABLE III:

TABLE X Ingredients OPTIONAL INTERMEDIATE CORE LAYER MATERIALS (Phr) Ex.5A Ex. 6A Ex. 7A Ex. 8A Primacor ® 5980I¹ 43 48 48 47 Fusabond ® N525²11 * 12 * Elvaloy ® AC 3427³ * * * 13 Kraton FG1924 G⁴ * 12 * * EthylOleate 10 * * * Oleic Acid 36 40 40 40 Mg(OH)₂ 8.0 8.9 8.9 8.8¹Primacor ® 5980I is an Ethylene/-Acrylic Acid Copolymer available fromDow Chemical Company. ²Fusabond ® N525 is an anhydride modified ethylenecopolymer available from E. I. du Pont de Nemours and Company, Inc.³Elvaloy ® AC 3427 is a copolymer of ethylene and butyl acrylateavailable from E. I. du Pont de Nemours and Company, Inc. ⁴Kraton FG1924G is a linear triblock copolymer based on styrene and ethylene/butylenewith a polystyrene content of 13% (Styrene block copolymer) availablefrom Kraton Polymers.

In one alternative embodiment, the Shore D hardness of the outersurface, plus 30, is greater than the center Shore C hardness by atleast 45. In another embodiment, the Shore D hardness of the outersurface, plus 30, is greater than the center Shore C hardness by atleast 50. In yet another embodiment, the Shore D hardness of the outersurface, plus 30, is greater than the center Shore C hardness by atleast 55. In yet another embodiment, the Shore D hardness of the outersurface, plus 30, is greater than the center Shore C hardness by atleast 60. In yet another embodiment, the Shore D hardness of the outersurface, plus 30, is greater than the center Shore C hardness by atleast 65.

In each and every different construction herein, inner core layer andouter core layer interface hardnesses may be determined as depicted inFIG. 1. Referring to FIG. 1, the interface hardness of a core layer isdefined herein as the extrapolated hardness from the curve produced bymaking hardness measurements on the cross-section of a core or ballradially outward from the center in about 2 mm increments. As shown inFIG. 1, the outer core interface hardness is then extrapolated byexamining that curve in a direction inward from outer core layer's outersurface. Meanwhile, the inner core interface hardness is extrapolated byexamining the curve in a direction radially outward from the inner corelayer's center.

Suitable Transparent or Plasticized Polvamide Compositions

The transparent polyamide by itself, may comprise a homopolymer,copolymers including block copolymer, or a blend or alloy thereof. Inone preferred embodiment, the composition further comprises an acidanhydride-modified polyolefin and/or plasticizer as discussed below.

The term, “polymer” refers to, but is not limited to, oligomers,homopolymers, copolymers, terpolymers, and the like. The polymers mayhave various structures including, but not limited to, regular,irregular, alternating, periodic, random, block, graft, linear,branched, isotactic, syndiotactic, atactic, and the like. Polyamidepolymers include, but are not limited to, polyamide copolymers(copolyamides) having two types of monomers, copolymers having threetypes of monomers, and copolymers having more than three types ofmonomers. Blends and alloys of polyamides also may be made in accordancewith this invention as described further below.

In general, transparent polyamides are classified as having amicrocrystalline structure or amorphous structure. Both microcrystallineand amorphous transparent polyamides may be used in the presentinvention. It should be understood that while a transparent polyamide ispreferably included in the composition, the final composition may have atransparent, translucent, or opaque optical nature. That is, the finalcomposition may contain various additives including fillers, coloringagents, dyes, pigments, and the like that effect the optical nature ofthe composition. By the term, “translucent,” as used herein, it is meanthaving a light transmission of greater than 1 percent per the testprocedures, ASTM D1003, using an Illuminate C light source.Alternatively, the polyamide composition has a transparency of at leastabout 50%, and more preferably within a range having a lower limit ofabout 50% or 55% or 60% or 65% or 70% and an upper limit of about 75% or80% or 85% or 90% or 95% or greater as measured by ISO 13468-1,2 using a2 mm thick sample measured at a wavelength of 560nm.

Examples of commercially available transparent polyamide polymers thatare suitable for use in an outer core layer of a golf ball of theinvention include the following: copolyamides such as Platamid® 8020;semi-aromatic transparent polyamides such as Rilsan® Clear G170;transparent polyamides such as Rilsan® G120 Rnew; Rilsan®G830 Rnew andG830 L Rnew; Rilsan® G850; Rilsan® Clear G350 and G350L; Rilsan® G300HI; and transparent polyamides that are partly based on bio-based rawmaterials such as Rilsan® Clear G830, all of which are available fromArkema, Inc. (King of Prussia, Pa.), may be used. Other suitableexamples include Ultramid® polyamides, available from BASF; and Zyteland Dartek nylon resins, available from DuPont. EMS-Chemie AG(Domat/EMS, Switzerland) supplies different grades of transparentpolyamides under the Grilamid mark, including; Grilamid® TR 30, TR55,TR90, XE 3997, XE 4028 grades, and these polyamides may be used per thisinvention. Grivory® G and GTR transparent polyamides also are availablefrom EMS-Chemie AG and may be used in the compositions of thisinvention.

Other suitable polyamides include for example Trogamid® and Vestamid®grades available from DeGussa AG (Marl, Germany); Kopa® grades availablefrom Kolon; Dureathan® grades available from Lanxess AG (Cologne,Germany); Arlen® grades available from Mitsui (Japan); transparentamorphous nylons such as Ashlene® D870 and D870L available from AshleyPolymers (Brooklyn, N.Y.); Radici Radilon® CST copolyamides (Italy);Shakespeare Isocor® CN30XT and CN30BT nylon 610 resins (ShakespeareEngineered Nylons owned by Jarden Applied Materials, Columbia, S.C.),Toyobo Glamide® T-714E nylons (Japan); and TP Composites Elastoblend®PA12 CL nylons (Aston, Pa.). Transparent polyamides including, but notlimited to, polyether-amide, polyester-amide, polyether-ester-amideblock copolymers, are particularly suitable for use in the inventionherein, and more particularly, the transparent polyamide copolymers,Rilsan Clear G300 HI, Pebax Clear 300, and Pebax Clear 400 availablefrom Arkema, Inc. (King of Prussia, Pa.) are particularly effective.

Meanwhile, examples of suitable transparent homopolyamides andcopolyamides, which are amorphous or exhibit a slight crystallinity, aredescribed in U.S. Pat. App. Publ. No. 2010/0140846; U.S. Pat. No.6,376,037 to Montanari et al.; and U.S. Pat. No. 8,399,557 to Montanariet al., the entire disclosures of which are hereby incorporated hereinby reference. Also, suitable amorphous transparent or translucentpolyamides that may be formed from the condensation of diamines withdicarboxylic acids or lactams; and blends or alloys of two or moredifferent polyamides, are described in U.S. Pat. App. Publ. No.2012/0223453, the entire disclosure of which is hereby incorporatedherein by reference.

Additionally, suitable polyamide copolymers such as a copolymerscontaining polyether blocks and polyamide blocks are described in U.S.Pat. App. Publ. No. 2013/0202831 (“831 Publ.”), the entire disclosure ofwhich is hereby incorporated herein by reference. The polyamidecopolymers described in the '831 Publ. have the following properties:are resistant to a high-velocity impact of at least 76.2 m/s (250 ft/s)according to the EN 166 standard; have a Charpy notched impact strengthof at least 90 kJ/m² according to the ISO 179 leU standard; preferablyalso have a chemical resistance such that it is capable of deforming, inflexion, by immersion in a solvent according to the ISO 22088-3 standardby at least 3% without breaking; are light, having a density of lessthan 1.05 g/cm³ measured according to the ISO 1183 D standard; and areflexible and have an elastic modulus of less than 1000 MPa, preferablyof less than 800 MPa, measured according to the ISO 527-2:93-1BAstandard.

Suitable transparent polyamides are further described in U.S. Pat. No.6,528,560 to Buhler; U.S. Pat. No. 6,831,136 to Torre et al.; U.S. Pat.No. 6,943,231 to Bühler; U.S. Pat. No. 8,309,643 to Thullen et al.; U.S.Pat. No. 8,507,598 to Bühler; and U.S. Pat. App. Publ. No. 2010/0203275,the entire disclosures of which are hereby incorporated herein byreference. In general, polyamides refer to high molecular weightpolymers in which amide linkages (—CONH-) occur along the length of themolecular chain (Hawley's Condensed Chemical Dictionary, 13^(th) Ed.).Suitable polyamides for use in the compositions of this invention may beobtained, for example, by: (1) polycondensation of (a) a dicarboxylicacid, such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, or decamethylenediamine,1,4-cyclohexyldiamine or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or w-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include, but are not limited to, nylon 6, nylon 6,6; nylon6,10; nylon 11, and nylon 12. Aliphatic and aromatic polyamides andblends thereof may be prepared in accordance with this invention.

In general, polyamide homopolymers and copolymers are suitable for usein this invention. The specific monomers, reaction conditions, and otherfactors will be selected based on the desired polyamide polymer to beproduced. There are two common methods for producing polyamidehomopolymers. In a first method, a compound containing one organicacid-type end group and one amine end group is formed into a cyclicmonomer. The polyamide is then formed from the monomer by a ring-openingpolymerization. These polyamides are commonly designated as nylon 6,nylon 11, nylon 12, and the like, where the number indicates the numberof carbon atoms making up the ring in the monomer. For example, nylon 6is a homopolymer of caprolactam, that is, polycaprolactam. The secondmethod involves the condensation polymerization of a dibasic acid and adiamine. In general, this reaction takes place as follows:

Conventional polyamides are commonly designated as nylon 4,6; nylon 6,6;nylon 6,9; nylon 6,10; nylon 6,12; and the like, where the first numberindicates the number of carbon atoms connecting the two amine groups inthe diamine and the second number indicates the number of carbon atomsconnecting the two acid groups in the dibasic acid, including those inthe acid groups. For example, nylon 6,6 is the reaction product ofhexamethylenediamine and adipic acid.

Other suitable polyamides include nylon 4, nylon 7, nylon 13, nylon12,12; nylon 13,13; and mixtures/blends thereof with suitablepolyamides. Still other polyamides include nylon 6/66; and nylon 6/69and mixtures/blends thereof with suitable polyamides. Polyamidecompositions having mechanical properties that do not significantlychange after the composition has been exposed to moisture areparticularly effective.

As noted above, transparent polyamides are particularly suitable for usein the invention herein. Such transparent polyamides include transparentpolyamide copolymers (copolyamides). For example, polyether-amide andpolyester-amide block copolymers may be used. Such polyamide copolymersare described, for example, in the above-mentioned U.S. Pat. App. Publ.No. 2010/0140846 and U.S. Pat. Nos. 6,376,037 and 8,399,557, the entiredisclosures of which are hereby incorporated herein by reference. Itshould be understood that the term, “polyamide” as used in the presentinvention, is meant to include copolymers with polyamide blocks andpolyether blocks, i.e., polyether block amide polymers, and the mixturesof these copolymers with the preceding polyamides. Polymers withpolyamide blocks and polyether blocks result from the copolycondensationof polyamide sequences comprising reactive ends with polyether sequencescomprising reactive ends, such as, inter alia:

-   -   a) polyamide sequences comprising diamine chain ends with        polyoxyalkylene sequences comprising dicarboxylic chain ends,    -   b) polyamide sequences comprising dicarboxylic chain ends with        polyoxyalkylene sequences comprising diamine chain ends obtained        by cyanoethylation and hydrogenation of αΩ-dihydroxylated        aliphatic polyoxyalkylene sequences, known as polyetherdiols,    -   c) polyamide sequences comprising dicarboxylic chain ends with        polyetherdiols, the products obtained being, in this specific        case, polyetheresteramides.

These polymers with polyamide blocks and polyether blocks, whether theyoriginate from the copolycondensation of polyamide and polyethersequences prepared beforehand or from a one-stage reaction, exhibit, forexample, Shore D hardnesses which can be from 20 to 95 andadvantageously between 25 and 85, more preferably 30 to 80, and evenmore preferably 35 to 78 and an intrinsic viscosity between 0.8 and 2.5,measured in meta-cresol at 25° C.

Whether the polyester blocks derive from polyethylene glycol,polyoxypropylene glycol or polyoxytetramethylene glycol, they are eitherused as is and copolycondensed with polyamide blocks comprisingcarboxylic ends or they are aminated, in order to be converted intopolyetherdiamines, and condensed with polyamide blocks comprisingcarboxylic ends. They can also be mixed with polyamide precursors and achain-limiting agent in order to form polymers with polyamide blocks andpolyether blocks having statistically distributed units. Polymers withpolyamide and polyether blocks are disclosed in U.S. Pat. Nos.4,331,786, 4,115,475, 4,195,015, 4,839,441, 4,864,014, 4,230,838 and4,332,920, the entire disclosures of which are hereby incorporatedherein by reference. The polyether can be, for example, a polyethyleneglycol (PEG), a polypropylene glycol (PPG) or a polytetramethyleneglycol (PTMG). The latter is also known as polytetrahydrofuran (PTHF).

Blends of polyamides also may be used in accordance with this invention.For example, a blend of transparent polyamides or a blend of transparentand non-transparent polyamides may be used in accordance with thisinvention. In particular, a blend of transparent polyamide and athermoplastic polyamide elastomer (typically a copolymer of polyamideand polyester / polyether) may be used. The polyamide elastomer may betransparent or non-transparent. Many polyamide elastomers comprise ahard polyamide segment (for example, nylon 6, nylon 6,6; nylon 11, nylon12 and the like) and a polyether or polyester as a soft segment.Suitable polyamide elastomers that can be used to form the compositionsof this invention include, for example. polyether-amide blockcopolymers, available from Arkema, Inc. (Columbs, France) as Pebax®resins. In general, these block copolymers have thermoplastic properties(softens when exposed to heat and returns to original condition whencooled) properties and elastomeric properties (can be stretched and thenreturns to a near original condition when released) properties. Theratio of hard to soft segments and the length, sequence, and like of thesegments are significant factors in determining the properties of theresulting block copolymer.

One advantageous property of the transparent polyamides used to form thecompositions of the present invention is that they exhibit a relativelyhigh glass transition temperature. The transparent polyamides arerelatively easy to process and can be molded to form different golf balllayers. In general, the glass-liquid transition refers to the reversibletransition in amorphous materials (or in the amorphous regions withinsemi-crystalline materials) from a hard and relatively brittle stateinto a molten or state. The glass transition temperature (T_(g)) asreported herein is measured according to Test Method ISO 11357 andreported in degrees celsius. As the temperature of a polymer drops belowT_(g), it behaves in an increasingly brittle manner. As the temperaturerises above the T_(g), the polymer becomes more rubber-like. Thus,knowledge of T_(g) is an important factor in the selection of materialsfor golf ball layer applications. In general, values of T_(g) well belowroom temperature define the domain of elastomers and values above roomtemperature define rigid, structural polymers. It has been found thatpreferred transparent polyamides exhibit a T_(g) in a range of about 30to about 170° C., and has a lower range of about 35° C. or 40° C. or 50°C. or 60C and an upper range of about 70° C. or 80° C. or 90° C. or 120°C. or 140° C. or or 150° C. In one preferred version, the T_(g) may beabout 65° C., 75° C., 85° C., 91° C., 95° C. or 105° C.

It is important to note that these preferred transparent polyamides mayalso have a second T_(g) that is observed at below ambient temperatures(less than 25° C.). It is believed that this sub-ambient T_(g) isassociated with a relatively soft polyether segment; whereas, the highertemperature T_(g) is associated with a polyamide segment. Therefore, inone embodiment, a transparent polyamide having a reported T_(g) of 90°C. may or may not also exhibit a T_(g) at -65° C., and the like. In oneembodiment, the transparent polyamide has a glass transition temperaturein the range of about 75° to about 160° C., more preferably in the rangeof about 80° to about 95° C.

As used herein, the term, “semi-crystalline” covers (co)polyamides whichhave both a glass transition temperature T_(g) and a melting point asdetermined by DSC. The term, “amorphous” covers polyamides that do nothave a melting point detected by DSC or a melting point with negligibleintensity such that it does not affect the essentially amorphous natureof the polymer. The term, “semi-crystalline”, as used herein, relates topolymers that have both a melting exotherm and a glass transition asdetermined by DSC. The term, “amorphous”, as used herein, relates topolymers that have a glass transition but do not exhibit a areessentially amorphous and exhibit a glass transition and a small orinsignificant melting exotherm (DH_(f)<=10 J/g) as determined by DSC.The term, “micro-crystalline”, as used herein, refers tosemi-crystalline polymers in which melting exotherm as determined byDSC. The term, “quasi-amorphous”, as used herein, relates to polymersthat the spherulite size is sufficiently small in order to maintaintransparency.

The transparent polyamides also have high flexibility, toughness,impact-durability and stress-crack resistance. One advantageous propertyof the transparent polyamides used to form the compositions of thepresent invention is their relatively high Charpy impact-resistance. Ingeneral, impact testing refers to the energy required to break or deforma material. The Charpy impact test is a standardized high strain-ratetest which determines the amount of energy absorbed by a material duringfracture. This absorbed energy is a measure of a given material's notchtoughness and acts as a tool to study temperature-dependentductile-brittle transition. The test method standard is ISO 179/1eA.Samples are conditioned for 15 days at 23° C. and 50% relative humidity.The test results herein are measured at either 23° C. or -30° C. andresults are reported in kilojoules per meter squared. The higher thenumber, the tougher the material, with a no-break (NB) meaning that thetest sample was flexible enough to withstand the impact withoutfracturing. High Charpy impact values are an important material propertyto consider when choosing a material for a layer in a golf ball, since agolf ball must withstand very high force impacts, such as thoseencountered when struck with a golf club. It is believed that thepolyamide compositions herein comprising a transparent polyamide,preferably have a Charpy notched impact (at 23° C.) of from at leastabout 8 to No-Break (NB), and have a lower range of from about 10 or 15or 20 or 25 or 30 or or 35 or 40 kJ/m² to an upper limit ranging fromabout 80, 85, 90, or 95 kJ/m² to no-break. A preferred transparentpolyamide composition comprises Rilsan Clear G300 HI, which has a Charpynotched impact value at 23° C. of 94 kJ/m², and a value at −30° C. of 19kJ/m².

The polyamide compositions of this invention may further contain acidanhydride-modified polyolefins. Adding the acid anhydride-modifiedpolyolefin helps improve the toughness and impact durability of thecomposition. In such materials, the polyolefin polymer is chemicallymodified with acid anhydride. That is, the polyolefin polymer isfunctionalized; it contains at least one acid anhydride group. Ingeneral, such acid anhydride groups may be grafted onto the polyolefinpolymer backbone. Some examples of suitable acid anhydrides that may beused to functionalize the polyolefin include, but are not limited to,fumaric, nadic, itaconic, and clorendic anhydrides, and theirsubstituted derivatives thereof.

Suitable olefin monomeric units that can be used to prepare thepolyolefin polymer include, for example, ethylene, propylene, butene,hexene, heptene, octene, decene, and dodecene. Preferably, the monomericunit contains from 2 to about 20 carbon atoms. The resulting polyolefinchains (polymer backbones) formed from these monomeric units include,for example, polyethylene, high density polyethylene (HDPE), low densitypolyethylene (LDPE), very low density polyethylene (VLDPE),polypropylene, polybutene, polyhexene, polyoctene, polydecene, andpolydodecene, and copolymers and blends thereof. The resultingpolyolefin polymer is functionalized with at least one acid anhydridemoiety. More particularly, the acid anhydride-modified polyolefinpolymers used in this invention include copolymers such as, for example,ethylene-based copolymers, particularly ethylene-propylene (EP);ethylene-butene (EB); ethylene-hexene (EH); ethylene-octene (EO);styrene-ethylene/butylene-styrene (SEBS); ethylene-propylene dienemonomer (EPDM); ethylene-vinyl acetate (EVA); and various ethylene-alkylacrylate and ethylene-alkyl alkyl acrylate copolymers such as, forexample, ethylene-methyl acrylate (EMA); ethylene- ethyl acrylate (EEA);ethylene-propyl acrylate (EPA); ethylene n-butyl acrylate (EBA)copolymers; and the like.

Other polyolefin-based copolymers such as polypropylene andpolybutene-based copolymers also can be used. These copolymers includerandom, block, and graft copolymers which have been functionalized withacid anhydride groups. Examples of commercially-available acid anhydridepolyolefins that can be used in accordance with this invention, include,but are not limited to, Amplify™ GR functional polymers, available fromthe Dow Chemical Company; Fusabond® polymers, available from the DuPontCompany; Kraton® FG and RP polymers, available from Kraton Polymers LLC;Lotader® polymers available from Arkema, Inc.; Polybond® and Royaltuf®polymers, available from Addivant.; and Exxelor polymers available fromthe ExxonMobil Corp.

Various polyamide compositions may be made in accordance with thisinvention. The composition may optionally contain an acidanhydride-modified polyolefin, plasticizer, fatty acid salt, fatty acidamide, fatty acid ester, and mixtures thereof. The resulting polyamidecomposition may be used to prepare a golf ball component (for example,core, casing, or cover layer) having several advantageous properties. Asnoted above, it is significant that a blend comprising transparentpolyamide and acid anhydride-modified polyolefin may be prepared and theresulting composition has excellent properties, particularly suitablefor making golf ball layers. For example, a blend of 90% Grivory™ GTR45transparent polyamide and 10% Fusabond™ N525 acid anhydride-modifiedpolyolefin may be prepared and the resulting composition (solid,transparent sphere) has a COR of 0.784, Atti Compression of 182, andShore

D surface hardness of 81.8. In another example, a blend of 50% Grivory™GTR45 transparent polyamide and 50% Fusabond™ N525 acidanhydride-modified polyolefin may be prepared and the resultingcomposition (solid, transparent sphere) has a COR of 0.633, AttiCompression of 105, and Shore D surface hardness of 56.2.

In other embodiments, it is not necessary for the polyamide to beblended with an acid anhydride-modified polyolefin or any other polymeror non-polymer material. That is, the composition may consist entirelyof the transparent polyamide (that is, 100% by weight polyamide). Inother instances, the composition may consist essentially of thetransparent polyamide (for example, 97 to 100% by weight polyamide).Such polyamide compositions may contain other ingredients that do notmaterially affect the basic and novel characteristics of thecomposition. For example, mineral fillers may be added as discussedfurther below. In one particular version, the composition consistsessentially of transparent polyether-amide block copolymer such as theabove-mentioned Rilsan G300 HI, Pebax Clear 300, or Pebax Clear 400(Arkema, Inc.).

In one embodiment, the polyamide compositions of the outer core layerfurther contain a plasticizer. Adding the plasticizers to thecomposition helps to reduce the glass transition temperature (T_(g)) ofthe composition. The glass transition in a polymer is a temperaturerange below which a polymer is relatively brittle and above which it isrubber-like. In addition to lowering the T_(g), the plasticizer may alsoreduce the tan εin the temperature range above the T_(g). A polymer'sT_(g) is measured by a Differential Scanning calorimeter or a DynamicMechanical Analyzer (DMA) and the DMA is used to measure tan δ. Theplasticizer may also reduce the hardness and compression of thecomposition when compared to its non-plasticized⁻condition. Adding theplasticizers to the composition also helps decrease the stiffness of thecomposition. That is, the plasticizer helps lower the flex modulus ofthe composition. The flex modulus refers to the ratio of stress tostrain within the elastic limit (when measured in the flexural mode) andis similar to tensile modulus. This property is used to indicate thebending stiffness of a material.

The flexural modulus, which is a modulus of elasticity, is determined bycalculating the slope of the linear portion of the stress-strain curveduring the bending test. If the slope of the stress-strain curve isrelatively steep, the material has a relatively high flexural modulusmeaning the material resists deformation. The material is more rigid. Ifthe slope is relatively flat, the material has a relatively low flexuralmodulus meaning the material is more easily deformed. The material ismore flexible. The flex modulus can be determined in accordance withASTM D790 standard among other testing procedures.

The polyamide compositions may contain one or more plasticizers. Theplasticizers that may be used in the polyamide compositions of thisinvention include, for example, N-butylbenzenesulfonamide (BBSA);N-ethylbenzenesulfonamide (EBSA); N-propylbenzenesulfonamide (PBSA);N-butyl-N-dodecylbenzenesulfonamide (BDBSA);N,N-dimethylbenzenesulfonamide (DMBSA); p-methylbenzenesulfonamide;o,p-toluene sulfonamide; p-toluene sulfonamide;2-ethylhexyl-4-hydroxybenzoate; hexadecyl-4-hydroxybenzoate;1-butyl-4-hydroxybenzoate; dioctyl phthalate; diisodecyl phthalate;di-(2-ethylhexyl)adipate; and tri-(2-ethylhexyl)phosphate.

Other suitable plasticizer compounds include benzene mono-, di-, andtricarboxylic acid esters. Phthalates such as Bis(2-ethylhexyl)phthalate(DEHP), Diisononyl phthalate (DINP), Di-n-butyl phthalate (DnBP, DBP),Butyl benzyl phthalate (BBP), Diisodecyl phthalate (DIDP), Dioctylphthalate (DnOP), Diisooctyl phthalate (DIOP), Diethyl phthalate (DEP),Diisobutyl phthalate (DIBP), and Di-n-hexyl phthalate are suitable. Iso-and terephthalates such as Dioctyl terephthalate and Dinonylisophthalate may be used. Also appropriate are trimellitates such asTrimethyl trimellitate (TMTM),Tri-(2-ethylhexyl) trimellitate(TOTM),Tri-(n-octyl,n-decyl)trimellitate, Tri-(heptyl,nonyl)trimellitate, Tri-n-octyl trimellitate; as well as benzoates, including:2-ethylhexyl-4-hydroxy benzoate, n-octyl benzoate, methyl benzoate, andethyl benzoate.

Also suitable are alkyl diacid esters commonly based on C4-C12 alkyldicarboxylic acids such as adipic, sebacic, azelaic, and maleic acidssuch as: Bis(2-ethylhexyl)adipate (DEHA), Dimethyl adipate (DMAD),Monomethyl adipate (MMAD), Dioctyl adipate (DOA), Dibutyl sebacate(DBS), Dibutyl maleate (DBM), Diisobutyl maleate (DIBM), Dioctylsebacate (DOS). Also, esters based on glycols, polyglycols andpolyhydric alcohols such as poly(ethylene glycol) mono- and di-esters,cyclohexanedimethanol esters, sorbitol derivatives; and triethyleneglycol dihexanoate, diethylene glycol di-2-ethylhexanoate, tetraethyleneglycol diheptanoate, and ethylene glycol dioleate may be used.

Fatty acids, fatty acid salts, fatty acid amides, and fatty acid estersalso may be used in the compositions of this invention. Compounds suchas stearic, oleic, ricinoleic, behenic, myristic, linoleic, palmitic,and lauric acid esters, salts, and mono- and bis-amides can be used.Methyl oleate, ethyl oleate, butyl oleat, 2-ethylhexyl oleate, octyloleate, butyl stearate, methyl acetylricinoleate, zinc oleate, ethylenebis-oleamide, and stearyl erucamide are suitable. Suitable fatty acidsalts include, for example, metal stearates, erucates, laurates,oleates, palmitates, pelargonates, and the like. For example, fatty acidsalts such as zinc stearate, calcium stearate, magnesium stearate,barium stearate, and the like can be used. Fatty alcohols and acetylatedfatty alcohols are also suitable, as are carbonate esters such aspropylene carbonate and ethylene carbonate.

Glycerol-based esters such as soy-bean, tung, or linseed oils or theirepoxidized derivatives can also be used as plasticizers in the presentinvention, as can polymeric polyester plasticizers formed from theesterification reaction of diacids and diglycols as well as from thering-opening polymerization reaction of caprolactones with diacids ordiglycols. Citrate esters and acetylated citrate esters are alsosuitable.

Dicarboxylic acid molecules containing both a carboxylic acid ester anda carboxylic acid salt can perform suitably as plasticizers. Themagnesium salt of mono-methyl adipate and the zinc salt of mono-octylglutarate are two such examples for this invention. Tri- andtetra-carboxylic acid esters and salts can also be used.

Also envisioned as suitable plasticizers are organophosphate andorganosulfur compounds such as Tricresyl phosphate (TCP), Tributylphosphate(TBP), alkyl sulfonic acid phenyl esters (ASE); andsulfonamides such as N-ethyl toluenesulfonamide,N-(2-hydroxypropyl)benzene sulfonamide, N-(n-butyl)benzenesulfonamide. Furthermore, thioester and thioether variants of theplasticizer compounds mentioned above are suitable. Non-esterplasticizers such as alcohols, polyhydric alcohols, glycols,polyglycols, and polyethers are suitable materials for plasticization.Materials such as polytetramethylene ether glycol, poly(ethyleneglycol), and poly(propylene glycol), oleyl alchohol, and cetyl alcoholcan be used. Hydrocarbon compounds, both saturated and unsaturated,linear or cyclic can be used such as mineral oils, microcrystallinewaxes, or low-molecular weight polybutadiene. Halogenated hydrocarboncompounds can also be used.

Other examples of polyamide plasticizers that may be used in thecomposition of this invention include butylbenzenesulphonamide (BBSA),ethylhexyl para-hydroxybenzoate (EHPB) and decylhexylpara-hydroxybenzoate (DHPB), as disclosed in Montanari et al., U.S. Pat.No. 6,376,037, the disclosure of which is hereby incorporated byreference.

Esters and alkylamides such as phthalic acid esters including dimethylphthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate,di-2-ethylhexyl phthalate, di-n-octyl phthalate, diisodecyl phthalate,ditridecyl phthalate, dicyclohexyl phthalate, butylbenzyl phthalate,diisononyl phthalate, ethylphthalylethyl glycolate, butylphthalylbutylglycolate, diundecyl phthalate, di-2-ethylhexyl tetrahydrophthalate asdisclosed in Isobe et al., U.S. Pat. No. 6,538,099, the disclosure ofwhich is hereby incorporated by reference, also may be used.

U.S. Pat. No. 7,045,185 to Jacques et al., the entire disclosure ofwhich is hereby incorporated herein by reference, discloses suitableplasticizers: sulphonamides such as N-butylbenzenesulphonamide,ethyltoluene-suiphonamide, N-cyclohexyltoluenesulphonamide,2-ethylhexyl-para-hydroxybenzoate, 2-decylhexyl-para-hydroxybenzoate,oligoethyleneoxytetrahydrofurfuryl alcohol, or oligoethyleneoxymalonate; esters of hydroxybenzoic acid; esters or ethers oftetrahydrofurfuryl alcohol, and esters of citric acid or hydroxymalonicacid.

Sulfonamides are particularly preferred plasticizers for use in thepresent invention as described, for example, in U.S. Pat. No. 7,297,737to Fish, Jr. et al., the entire disclosure of which is herebyincorporated herein by reference. Examples of such sulfonamides includeN-alkyl benzenesulfonamides and toluenesufonamides, particularlyN-butylbenzenesulfonamide, N-(2-hydroxypropyl)benzenesulfonamide,N-ethyl-o-toluenesulfonamide, N-ethyl-p-toluenesulfonamide,o-toluenesulfonamide, p-toluenesulfonamide. Such sulfonamideplasticizers also are described in Hochstetter et al., U.S. Pat. App.Publ. No. 2010/0183837, the entire disclosure of which is herebyincorporated herein by reference. The polyamide compositions containingplasticizer, as described in the above patent references, also may beused in this invention.

Intermediate Layers and Cover Layers

The optional intermediate layer(s) of golf balls such as those depictedherein, whether disposed between the inner core layer and outer corelayer, or disposed between the outer core layer and cover, are notlimited by a particular composition for forming the layer(s), and can beformed from any suitable golf ball composition

An optional core intermediate layer may in one embodiment be made from acomposition including at least one thermoset base rubber, such as apolybutadiene rubber, cured with at least one peroxide and at least onereactive co-agent, which can be a metal salt of an unsaturatedcarboxylic acid, such as acrylic acid or methacrylic acid, anon-metallic coagent, or mixtures thereof. Preferably, a suitableantioxidant is included in the composition. An optional soft and fastagent (and sometimes a cis-to-trans catalyst), such as an organosulfuror metal-containing organosulfur compound, can also be included in thecore formulation.

The degree of crosslinking of the rubber may be increased by increasingthe amount (phr) of peroxide added. Meanwhile, zinc diacrylate is acoagent commonly used with peroxide to increase the state of cure, totake part in the cross-linking of polybutadiene. A small amount of ZDAand/or ZDMA produces a golf ball core with lower initial velocity andlower compression than a larger amount of coagent. The use of ZDAcoagent may increase velocity and hardness and contribute to a hardfeel. Thus, the amount of peroxide initiator and coagent can be variedto achieve a desired hardness. Antioxidants are compounds that inhibitor prevent the oxidative breakdown of elastomers, and/or inhibit orprevent reactions that are promoted by oxygen radicals.

Other ingredients that are known to those skilled in the art may beused, and are understood to include, but not be limited to,density-adjusting fillers, process aides, plasticizers, blowing orfoaming agents, sulfur accelerators, and/or non-peroxide radicalsources. The base thermoset rubber, which can be blended with otherrubbers and polymers, typically includes a natural or synthetic rubber.A preferred base rubber is 1,4-polybutadiene having a cis structure ofat least 40%, preferably greater than 80%, and more preferably greaterthan 90%. Examples of desirable polybutadiene rubbers include BUNA® CB22and BUNA® CB23, commercially available from LANXESS Corporation; UBEPOL®360L and UBEPOL® 150L and UBEPOL-BR rubbers, commercially available fromUBE Industries, Ltd. of Tokyo, Japan; BUDENE 1208, 1207, commerciallyavailable from Goodyear of Akron, Ohio; and CB BUNA® 1203G1, 1220, and1221, commercially available from LANXESS Corporation; Europrene®NEOCIS® BR 40 and BR 60, commercially available from Polimeri Europa;and BR 01, BR 730, BR 735, BR 11, and BR 51, commercially available fromJapan Synthetic Rubber Co., Ltd; and KARBOCHEM® ND40, ND45, and ND60,commercially available from Karbochem.

The base rubber may also comprise high or medium Mooney viscosityrubber, or blends thereof. A “Mooney” unit is a unit used to measure theresistance to flow of raw or unvulcanized rubber. The viscosity in a“Mooney” unit is equal to the torque, measured on an arbitrary scale, ona disk in a vessel that contains rubber at a temperature of 100° C. androtates at two revolutions per minute. The measurement of Mooneyviscosity is defined according to ASTM D-1646.

The Mooney viscosity range is preferably greater than about 40, morepreferably in the range from about 40 to about 80 and more preferably inthe range from about 40 to about 60. Polybutadiene rubber with higherMooney viscosity may also be used, so long as the viscosity of thepolybutadiene does not reach a level where the high viscositypolybutadiene adversely interferes with the manufacturing machinery. Itis contemplated that polybutadiene with viscosity less than 65 Mooneycan be used with the present invention.

In one embodiment of the present invention, golf ball cores made withmid- to high-Mooney viscosity polybutadiene material exhibit increasedresiliency (and, therefore, distance) without increasing the hardness ofthe ball. Such cores are soft, i.e., compression less than about 60 andmore specifically in the range of about 50-55. Cores with compression inthe range of from about 30 about 50 are also within the range of thispreferred embodiment. Commercial sources of suitable mid- to high-Mooneyviscosity polybutadiene include LANXESS CB23 (Nd-catalyzed), which has aMooney viscosity of around 50 and is a highly linear polybutadiene. Ifdesired, the polybutadiene can also be mixed with other elastomers knownin the art, such as other polybutadiene rubbers, natural rubber, styrenebutadiene rubber, and/or isoprene rubber in order to further modify theproperties of the core. When a mixture of elastomers is used, theamounts of other constituents in the core composition are typicallybased on 100 parts by weight of the total elastomer mixture.

In one preferred embodiment, the base rubber comprises an Nd-catalyzedpolybutadiene, a non-rare earth-catalyzed polybutadiene rubber, orblends thereof. If desired, the polybutadiene can also be mixed withother elastomers known in the art such as natural rubber, polyisoprenerubber and/or styrene-butadiene rubber in order to modify the propertiesof the core. Other suitable base rubbers include thermosetting materialssuch as, ethylene propylene diene monomer rubber, ethylene propylenerubber, butyl rubber, halobutyl rubber, hydrogenated nitrile butadienerubber, nitrile rubber, and silicone rubber.

Thermoplastic elastomers (TPE) may also be used to modify the propertiesof the core layers, or the uncured core layer stock by blending with thebase thermoset rubber. These TPEs include styrenic block copolymers,such as styrene ethylene butadiene styrene, styrene-isoprene-styrene,etc., a metallocene or other single-site catalyzed polyolefin such asethylene-octene, or ethylene-butene, or thermoplastic polyurethanes(TPU), including copolymers. Other suitable TPEs for blending with thethermoset rubbers of the present invention include PEBAX®, which isbelieved to comprise polyether amide copolymers, HYTREL®, which isbelieved to comprise polyether ester copolymers, thermoplastic urethane,and KRATON®, which is believed to comprise styrenic block copolymerselastomers. Any of the TPEs or TPUs above may also contain functionalitysuitable for grafting, including maleic acid or maleic anhydride.

Additional polymers may also optionally be incorporated into the baserubber. Examples include, but are not limited to, thermoset elastomerssuch as core regrind, thermoplastic vulcanizate, copolymeric ionomer,terpolymeric ionomer, polycarbonate, polyamide, copolymeric polyamide,polyesters, polyvinyl alcohols, acrylonitrile-butadiene-styrenecopolymers, polyarylate, polyacrylate, polyphenylene ether,impact-modified polyphenylene ether, high impact polystyrene, diallylphthalate polymer, styrene-acrylonitrile polymer (SAN) (includingolefin-modified SAN and acrylonitrile-styrene-acrylonitrile polymer),styrene-maleic anhydride copolymer, styrenic copolymer, functionalizedstyrenic copolymer, functionalized styrenic terpolymer, styrenicterpolymer, cellulose polymer, liquid crystal polymer, ethylene-vinylacetate copolymers, polyurea, and polysiloxane or anymetallocene-catalyzed polymers of these species.

Suitable polyamides for use as an additional polymeric material incompositions within the scope of the present invention also includeresins obtained by: (1) polycondensation of (a) a dicarboxylic acid,such as oxalic acid, adipic acid, sebacic acid, terephthalic acid,isophthalic acid, or 1,4-cyclohexanedicarboxylic acid, with (b) adiamine, such as ethylenediamine, tetramethylenediamine,pentamethylenediamine, hexamethylenediamine, or decamethylenediamine,1,4-cyclohexanediamine, or m-xylylenediamine; (2) a ring-openingpolymerization of cyclic lactam, such as ε-caprolactam or Ω-laurolactam;(3) polycondensation of an aminocarboxylic acid, such as 6-aminocaproicacid, 9-aminononanoic acid, 11-aminoundecanoic acid, or12-aminododecanoic acid; or (4) copolymerization of a cyclic lactam witha dicarboxylic acid and a diamine. Specific examples of suitablepolyamides include NYLON 6, NYLON 66, NYLON 610, NYLON 11, NYLON 12,copolymerized NYLON, NYLON MXD6, and NYLON 46.

Suitable peroxide initiating agents include dicumyl peroxide;2,5-dimethyl-2,5-di(t-butylperoxy)hexane;2,5-dimethyl-2,5-di(t-butylperoxy)hexyne;2,5-dimethyl-2,5-di(benzoylperoxy)hexane;2,2’-bis(t-butylperoxy)-di-iso-propylbenzene;1,1-bis(t-butylperoxy)-3,3,5-trimethyl cyclohexane; n-butyl4,4-bis(t-butyl-peroxy)valerate; t-butyl perbenzoate; benzoyl peroxide;n-butyl 4,4′-bis(butylperoxy) valerate; di-t-butyl peroxide; or2,5-di-(t-butylperoxy)-2,5-dimethyl hexane, lauryl peroxide, t-butylhydroperoxide, a-a bis(t-butylperoxy)diisopropylbenzene,di(2-t-butyl-peroxyisopropyl)benzene, di-t-amyl peroxide, di-t-butylperoxide. Preferably, the rubber composition includes from about 0.25 toabout 5.0 parts by weight peroxide per 100 parts by weight rubber (phr),more preferably 0.5 phr to 3 phr, most preferably 0.5 phr to 1.5 phr. Ina most preferred embodiment, the peroxide is present in an amount ofabout 0.8 phr. These ranges of peroxide are given assuming the peroxideis 100% active, without accounting for any carrier that might bepresent. Because many commercially available peroxides are sold alongwith a carrier compound, the actual amount of active peroxide presentmust be calculated. Commercially-available peroxide initiating agentsinclude DICUP™ family of dicumyl peroxides (including DICUP™ R, DICUP™40C and DICUP™ 40KE) available from ARKEMA. Similar initiating agentsare available from AkroChem, Lanxess, Flexsys/Harwick and R. T.Vanderbilt. Another commercially-available and preferred initiatingagent is TRIGONOX™ 265-50B from Akzo Nobel, which is a mixture of1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane anddi(2-t-butylperoxyisopropyl)benzene. TRIGONOX™ peroxides are generallysold on a carrier compound.

Suitable reactive co-agents include, but are not limited to, metal saltsof diacrylates, dimethacrylates, and monomethacrylates suitable for usein this invention include those wherein the metal is zinc, magnesium,calcium, barium, tin, aluminum, lithium, sodium, potassium, iron,zirconium, and bismuth. Zinc diacrylate (ZDA) is preferred, but thepresent invention is not limited thereto. ZDA provides golf balls with ahigh initial velocity. The ZDA can be of various grades of purity. Forthe purposes of this invention, the lower the quantity of zinc stearatepresent in the ZDA the higher the ZDA purity. ZDA containing less thanabout 10% zinc stearate is preferable. More preferable is ZDA containingabout 4-8% zinc stearate. Suitable, commercially available zincdiacrylates include those from Cray Valley. The preferred concentrationsof ZDA that can be used are about 10 phr to about 40 phr, morepreferably 20 phr to about 35 phr, most preferably 25 phr to about 35phr. In a particularly preferred embodiment, the reactive co-agent ispresent in an amount of about 29 phr to about 31 phr.

Additional preferred co-agents that may be used alone or in combinationwith those mentioned above include, but are not limited to,trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, andthe like. It is understood by those skilled in the art, that in the casewhere these co-agents may be liquids at room temperature, it may beadvantageous to disperse these compounds on a suitable carrier topromote ease of incorporation in the rubber mixture.

Antioxidants are compounds that inhibit or prevent the oxidativebreakdown of elastomers, and/or inhibit or prevent reactions that arepromoted by oxygen radicals. Some exemplary antioxidants that may beused in the present invention include, but are not limited to, quinolinetype antioxidants, amine type antioxidants, and phenolic typeantioxidants. A preferred antioxidant is2,2′-methylene-bis-(4-methyl-6-t-butylphenol) available as VANOX® MBPCfrom R. T. Vanderbilt. Other polyphenolic antioxidants include VANOX® T,VANOX® L, VANOX® SKT, VANOX® SWP, VANOX® 13 and VANOX® 1290.

Suitable antioxidants include, but are not limited to,alkylene-bis-alkyl substituted cresols, such as4,4′-methylene-bis(2,5-xylenol); 4,4′-ethylidene-bis-(6-ethyl-m-cresol);4,4′-butylidene-bis-(6 -t-butyl-m-cresol);4,4′-decylidene-bis-(6-methyl-m-cresol);4,4′-methylene-bis-(2-amyl-m-cresol);4,4′-propylidene-bis-(5-hexyl-m-cresol);3,3′-decylidene-bis-(5-ethyl-p-cresol);2,2′-butylidene-bis-(3-n-hexyl-p-cresol);4,4′-(2-butylidene)-bis-(6-t-butyl-m-cresol);3,3′-4(decylidene)-bis-(5-ethyl-p-cresol);(2,5-dimethyl-4-hydroxyphenyl) (2-hydroxy-3,5-dimethylphenyl)methane;(2-methyl-4-hydroxy-5-ethylphenyl)(2-ethyl-3-hydroxy-5-methylphenyl)methane;(3-methyl-5-hydroxy-6-t-butylphenyl)(2-hydroxy-4-methyl-5-decylphenyl)-n-butyl methane;(2-hydroxy-4-ethyl-5-methylphenyl)(2-decyl-3-hydroxy-4-methylphenyl)butylamylmethane;(3-ethyl-4-methyl-5-hydroxyphenyl)-(2,3-dimethyl-3-hydroxy-phenyl)nonylmethane;(3-methyl-2-hydroxy-6-ethylphenyl)-(2-isopropyl-3-hydroxy-5-methyl-phenyl)cyclohexylmethane;(2-methyl-4-hydroxy-5-methylphenyl)(2-hydroxy-3-methyl-5-ethylphenyl)dicyclohexyl methane; and the like.

Other suitable antioxidants include, but are not limited to, substitutedphenols, such as 2-tert-butyl-4-methoxyphenol;3-tert-butyl-4-methoxyphenol; 3-tert-octyl-4-methoxyphenol;2-methyl-4-methoxyphenol; 2-stearyl-4-n-butoxyphenol;3-t-butyl-4-stearyloxyphenol; 3-lauryl-4-ethoxyphenol;2,5-di-t-butyl-4-methoxyphenol; 2-methyl-4-methoxyphenol;2-(1-methycyclohexyl)-4-methoxyphenol; 2-t-butyl-4-dodecyloxyphenol;2-(1-methylbenzyl)-4-methoxyphenol; 2-t-octyl-4-methoxyphenol; methylgallate; n-propyl gallate; n-butyl gallate; lauryl gallate; myristylgallate; stearyl gallate; 2,4,5-trihydroxyacetophenone;2,4,5-trihydroxy-n-butyrophenone; 2,4,5-trihydroxystearophenone;2,6-ditert-butyl-4-methylphenol; 2,6-ditert-octyl-4-methylphenol;2,6-ditert-butyl-4-stearylphenol; 2-methyl-4-methyl-6-tert-butylphenol;2,6-distearyl-4-methylphenol; 2,6-dilauryl-4-methylphenol;2,6-di(n-octyl)-4-methylphenol; 2,6-di(n-hexadecyl)-4-methylphenol;2,6-di(1-methylundecyl)-4-methylphenol;2,6-di(1-methylheptadecyl)-4-methylphenol;2,6-di(trimethylhexyl)-4-methylphenol;2,6-di(1,1,3,3-tetramethyloctyl)-4-methylphenol; 2-n-dodecyl-6-tertbutyl-4-methylphenol; 2-n-dodecyl-6-(1-methylundecyl)-4-methylphenol;2-n-dodecyl-6-(1,1,3,3-tetramethyloctyl)-4-methylphenol;2-n-dodecyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-n-octyl-4-methylphenol;2-methyl-6-n-octadecyl-4-methylphenol;2-n-dodecyl-6-(1-methylheptadecyl)-4-methylphenol;2,6-di(1-methylbenzyl)-4-methylphenol;2,6-di(1-methylcyclohexyl)-4-methylphenol;2,6-(1-methylcyclohexyl)-4-methylphenol;2-(1-methylbenzyl)-4-methylphenol; and related substituted phenols.

More suitable antioxidants include, but are not limited to, alkylenebisphenols, such as 4,4′-butylidene bis(3-methyl-6-t-butyl phenol);2,2-butylidene bis (4,6-dimethyl phenol); 2,2′-butylidenebis(4-methyl-6-t-butyl phenol); 2,2′-butylidene bis(4-t-butyl-6-methylphenol); 2,2′-ethylidene bis(4-methyl-6-t-butylphenol); 2,2′-methylenebis(4,6-dimethyl phenol); 2,2′-methylene bis(4-methyl-6-t-butyl phenol);2,2′-methylene bis(4-ethyl-6-t-butyl phenol); 4,4′-methylenebis(2,6-di-t-butyl phenol); 4,4′-methylene bis(2-methyl-6-t-butylphenol); 4,4′-methylene bis(2,6-dimethyl phenol); 2,2′-methylenebis(4-t-butyl-6-phenyl phenol);2,2′-dihydroxy-3,3′,5,5′-tetramethylstilbene; 2,2′-isopropylidenebis(4-methyl-6-t-butyl phenol); ethylene bis (beta-naphthol);1,5-dihydroxy naphthalene; 2,2′-ethylene bis (4-methyl-6-propyl phenol);4,4′-methylene bis(2-propyl-6-t-butyl phenol); 4,4′-ethylene bis(2-methyl-6-propyl phenol); 2,2′-methylene bis(5-methyl-6-t-butylphenol); and 4,4′-butylidene bis(6-t-butyl-3-methyl phenol);

Suitable antioxidants further include, but are not limited to, alkylenetrisphenols, such as 2,6-bis (2′-hydroxy-3′-t-butyl-5′-methylbenzyl)-4-methyl phenol; 2,6-bis (2′-hydroxy-3′-t-ethyl-5′-butylbenzyl)-4-methyl phenol; and 2,6-bis(2′-hydroxy-3′-t-butyl-5′-propylbenzyl)-4-methyl phenol.

The antioxidant is typically present in an amount of about 0.1 phr toabout 5 phr, preferably from about 0.1 phr to about 2 phr, morepreferably about 0.1 phr to about 1 phr. In a particularly preferredembodiment, the antioxidant is present in an amount of about 0.4 phr. Inan alternative embodiment, the antioxidant should be present in anamount to ensure that the hardness gradient of the inventive cores isnegative. Preferably, about 0.2 phr to about 1 phr antioxidant is addedto the core layer (inner core or outer core layer) formulation, morepreferably, about 0.3 to about 0.8 phr, and most preferably 0.4 to about0.7 phr. Preferably, about 0.25 phr to about 1.5 phr of peroxide ascalculated at 100% active can be added to the core formulation, morepreferably about 0.5 phr to about 1.2 phr, and most preferably about 0.7phr to about 1.0 phr. The ZDA amount can be varied to suit the desiredcompression, spin and feel of the resulting golf ball. The cure regimecan have a temperature range between from about 290° F. to about 360°F., or from about 290° F. to about 335° F., or from about 300° F. toabout 325° F., or from about 330° F. to about 355° F., and the stock isheld at that temperature for at least about 10 minutes to about 30minutes.

The thermoset rubber composition in a core of the golf ball of thepresent invention may also include an optional soft and fast agent. Asused herein, “soft and fast agent” means any compound or a blend thereofthat that is capable of making a core 1) be softer (lower compression)at constant COR or 2) have a higher COR at equal compression, or anycombination thereof, when compared to a core equivalently preparedwithout a soft and fast agent. Preferably, the composition of thepresent invention contains from about 0.05 phr to about 10.0 phr softand fast agent. In one embodiment, the soft and fast agent is present inan amount of about 0.05 phr to about 3.0 phr, preferably about 0.05 phrto about 2.0 phr, more preferably about 0.05 phr to about 1.0 phr. Inanother embodiment, the soft and fast agent is present in an amount ofabout 2.0 phr to about 5.0 phr, preferably about 2.35 phr to about 4.0phr, and more preferably about 2.35 phr to about 3.0 phr. In analternative high concentration embodiment, the soft and fast agent ispresent in an amount of about 5.0 phr to about 10.0 phr, more preferablyabout 6.0 phr to about 9.0 phr, most preferably about 7.0 phr to about8.0 phr. In a most preferred embodiment, the soft and fast agent ispresent in an amount of about 2.6 phr.

Suitable soft and fast agents include, but are not limited to,organosulfur or metal-containing organosulfur compounds, an organicsulfur compound, including mono, di, and polysulfides, a thiol, ormercapto compound, an inorganic sulfide compound, a Group VIA compound,or mixtures thereof. The soft and fast agent component may also be ablend of an organosulfur compound and an inorganic sulfide compound.

Suitable soft and fast agents of the present invention include, but arenot limited to those having the following general formula:

where R₁-R₅ can be C₁-C₈ alkyl groups; halogen groups; thiol groups(—SH), carboxylated groups; sulfonated groups; and hydrogen; in anyorder; and also pentafluorothiophenol; 2-fluorothiophenol;3-fluorothiophenol; 4-fluorothiophenol; 2,3-fluorothiophenol;2,4-fluorothiophenol; 3,4-fluorothiophenol; 3,5-fluorothiophenol2,3,4-fluorothiophenol; 3,4,5-fluorothiophenol;2,3,4,5-tetrafluorothiophenol; 2,3,5,6-tetrafluorothiophenol;4-chlorotetrafluorothiophenol; pentachlorothiophenol;2-chlorothiophenol; 3-chlorothiophenol; 4-chlorothiophenol;2,3-chlorothiophenol; 2,4-chlorothiophenol; 3,4-chlorothiophenol;3,5-chlorothiophenol; 2,3,4-chlorothiophenol; 3,4,5-chlorothiophenol;2,3,4,5-tetrachlorothiophenol; 2,3,5,6-tetrachlorothiophenol;pentabromothiophenol; 2-bromothiophenol; 3-bromothiophenol;4-bromothiophenol; 2,3-bromothiophenol; 2,4-bromothiophenol;3,4-bromothiophenol; 3,5-bromothiophenol; 2,3,4-bromothiophenol;3,4,5-bromothiophenol; 2,3,4,5-tetrabromothiophenol;2,3,5,6-tetrabromothiophenol; pentaiodothiophenol; 2-iodothiophenol;3-iodothiophenol; 4-iodothiophenol; 2,3-iodothiophenol;2,4-iodothiophenol; 3,4-iodothiophenol; 3,5-iodothiophenol;2,3,4-iodothiophenol; 3,4,5-iodothiophenol; 2,3,4,5-tetraiodothiophenol;2,3,5,6-tetraiodothiophenoland; and their zinc salts. Preferably, thehalogenated thiophenol compound is pentachlorothiophenol, which iscommercially available in neat form or under the tradename STRUKTOL®, aclay-based carrier containing the sulfur compound pentachlorothiophenolloaded at 45 percent (correlating to 2.4 parts PCTP). STRUKTOL® iscommercially available from Struktol Company of America of Stow, Ohio.PCTP is commercially available in neat form from eChinachem of SanFrancisco, Calif. A and in the salt form from eChinachem of SanFrancisco, Calif. Most preferably, the halogenated thiophenol compoundis the zinc salt of pentachlorothiophenol, which is commerciallyavailable from eChinachem of San Francisco, Calif.

As used herein when referring to the invention, the term “organosulfurcompound(s)” refers to any compound containing carbon, hydrogen, andsulfur, where the sulfur is directly bonded to at least 1 carbon. Asused herein, the term “sulfur compound” means a compound that iselemental sulfur, polymeric sulfur, or a combination thereof. It shouldbe further understood that the term “elemental sulfur” refers to thering structure of S₈ and that “polymeric sulfur” is a structureincluding at least one additional sulfur relative to elemental sulfur.

Additional suitable examples of soft and fast agents (that are alsobelieved to be cis-to-trans catalysts) include, but are not limited to,4,4′-diphenyl disulfide; 4,4′-ditolyl disulfide; 2,2′-benzamido diphenyldisulfide; bis(2-aminophenyl)disulfide; bis(4-aminophenyl)disulfide;bis(3-aminophenyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide;2,2′-bis(3-aminonaphthyl)disulfide; 2,2′-bis(4-aminonaphthyl)disulfide;2,2′-bis(5-aminonaphthyl)disulfide; 2,2′-bis(6-aminonaphthyl)disulfide;2,2′-bis(7-aminonaphthyl)disulfide; 2,2′-bis(8-aminonaphthyl)disulfide;1,1′-bis(2-aminonaphthyl)disulfide; 1,1′-bis(3-aminonaphthyl)disulfide;1,1′-bis(3-aminonaphthyl)disulfide; 1,1′-bis(4-aminonaphthyl)disulfide;1,1′-bis(5-aminonaphthyl)disulfide; 1,1′-bis(6-aminonaphthyl)disulfide;1,1′-bis(7-aminonaphthyl)disulfide; 1,1′-bis(8-aminonaphthyl)disulfide;1,2′-diamino-1,2′-dithiodinaphthalene;2,3′-diamino-1,2′-dithiodinaphthalene; bis(4-chlorophenyl)disulfide;bis(2-chlorophenyl)disulfide; bis(3-chlorophenyl)disulfide;bis(4-bromophenyl)disulfide; bis(2-bromophenyl)disulfide;bis(3-bromophenyl)disulfide; bis(4-fluorophenyl)disulfide;bis(4-iodophenyl)disulfide; bis(2,5-dichlorophenyl)disulfide;bis(3,5-dichlorophenyl)disulfide; bis (2,4-dichlorophenyl)disulfide;bis(2,6-dichlorophenyl)disulfide; bis(2,5-dibromophenyl)disulfide;bis(3,5-dibromophenyl)disulfide; bis(2-chloro-5-bromophenyl)disulfide;bis(2,4,6-trichlorophenyl)disulfide;bis(2,3,4,5,6-pentachlorophenyl)disulfide; bis(4-cyanophenyl)disulfide;bis(2-cyanophenyl)disulfide; bis(4-nitrophenyl)disulfide;bis(2-nitrophenyl)disulfide; 2,2′-dithiobenzoic acid ethylester;2,2′-dithiobenzoic acid methylester; 2,2′-dithiobenzoic acid;4,4′-dithiobenzoic acid ethylester; bis(4-acetylphenyl)disulfide;bis(2-acetylphenyl)disulfide; bis(4-formylphenyl)disulfide;bis(4-carbamoylphenyl)disulfide; 1,1′-dinaphthyl disulfide;2,2′-dinaphthyl disulfide; 1,2′-dinaphthyl disulfide;2,2′-bis(1-chlorodinaphthyl)disulfide;2,2′-bis(1-bromonaphthyl)disulfide; 1,1′-bis(2-chloronaphthyl)disulfide;2,2′-bis(1-cyanonaphthyl)disulfide; 2,2′-bis(1-acetylnaphthyl)disulfide;and the like; or a mixture thereof. Preferred organosulfur componentsinclude 4,4′-diphenyl disulfide, 4,4′-ditolyl disulfide, or2,2′-benzamido diphenyl disulfide, or a mixture thereof. A morepreferred organosulfur component includes 4,4′-ditolyl disulfide. Inanother embodiment, metal-containing organosulfur components can be usedaccording to the invention. Suitable metal-containing organosulfurcomponents include, but are not limited to, cadmium, copper, lead, andtellurium analogs of diethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof.

Suitable substituted or unsubstituted aromatic organic components thatdo not include sulfur or a metal include, but are not limited to,4,4′-diphenyl acetylene, azobenzene, or a mixture thereof. The aromaticorganic group preferably ranges in size from C₆ to C₂₀, and morepreferably from C₆ to C₁₀. Suitable inorganic sulfide componentsinclude, but are not limited to titanium sulfide, manganese sulfide, andsulfide analogs of iron, calcium, cobalt, molybdenum, tungsten, copper,selenium, yttrium, zinc, tin, and bismuth.

A substituted or unsubstituted aromatic organic compound is alsosuitable as a soft and fast agent. Suitable substituted or unsubstitutedaromatic organic components include, but are not limited to, componentshaving the formula (R ₁)_(x)—R₃-M-R₄—(R₂)_(y), wherein R₁ and R₂ areeach hydrogen or a substituted or unsubstituted C₁₋₂₀ linear, branched,or cyclic alkyl, alkoxy, or alkylthio group, or a single, multiple, orfused ring C₆ to C₂₄ aromatic group; x and y are each an integer from 0to 5; R₃ and R₄ are each selected from a single, multiple, or fused ringC₆ to C₂₄ aromatic group; and M includes an azo group or a metalcomponent. R₃ and R₄ are each preferably selected from a C₆ to C₁₀aromatic group, more preferably selected from phenyl, benzyl, naphthyl,benzamido, and benzothiazyl. R₁ and R₂ are each preferably selected froma substituted or unsubstituted C₁₋₁₀ linear, branched, or cyclic alkyl,alkoxy, or alkylthio group or a C₆ to C₁₀ aromatic group. When R₁, R₂,R₃, or R₄, are substituted, the substitution may include one or more ofthe following substituent groups: hydroxy and metal salts thereof;mercapto and metal salts thereof; halogen; amino, nitro, cyano, andamido; carboxyl including esters, acids, and metal salts thereof; silyl;acrylates and metal salts thereof; sulfonyl or sulfonamide; andphosphates and phosphites. When M is a metal component, it may be anysuitable elemental metal available to those of ordinary skill in theart. Typically, the metal will be a transition metal, althoughpreferably it is tellurium or selenium. In one embodiment, the aromaticorganic compound is substantially free of metal, while in anotherembodiment the aromatic organic compound is completely free of metal.

The soft and fast agent can also include a Group VIA component.Elemental sulfur and polymeric sulfur are commercially available fromElastochem, Inc. of Chardon, Ohio. Exemplary sulfur catalyst compoundsinclude PB(RM-S)-80 elemental sulfur and PB(CRST)-65 polymeric sulfur,each of which is available from Elastochem, Inc. An exemplary telluriumcatalyst under the tradename TELLOY® and an exemplary selenium catalystunder the tradename VANDEX® are each commercially available from RTVanderbilt.

Fillers may also be added to the thermoset rubber composition of thecore to adjust the density of the composition, up or down. Typically,fillers include materials such as tungsten, zinc oxide, barium sulfate,silica, calcium carbonate, zinc carbonate, metals, metal oxides andsalts, regrind (recycled core material typically ground to about 30 meshparticle), high-Mooney-viscosity rubber regrind, trans-regrind corematerial (recycled core material containing high trans- isomer ofpolybutadiene), and the like. When trans-regrind is present, the amountof trans- isomer is preferably between about 10% and about 60%. In apreferred embodiment of the invention, the core comprises polybutadienehaving a cis- isomer content of greater than about 95% and trans-regrindcore material (already vulcanized) as a filler. Any particle sizetrans-regrind core material is sufficient, but is preferably less thanabout 125 pm.

Fillers added to one or more portions of the golf ball typically includeprocessing aids or compounds to affect rheological and mixingproperties, density-modifying fillers, tear strength, or reinforcementfillers, and the like. The fillers are generally inorganic, and suitablefillers include numerous metals or metal oxides, such as zinc oxide andtin oxide, as well as barium sulfate, zinc sulfate, calcium carbonate,barium carbonate, clay, tungsten, tungsten carbide, an array of silicas,and mixtures thereof. Fillers may also include various foaming agents orblowing agents which may be readily selected by one of ordinary skill inthe art. Fillers may include polymeric, ceramic, metal, and glassmicrospheres may be solid or hollow, and filled or unfilled. Fillers aretypically also added to one or more portions of the golf ball to modifythe density thereof to conform to uniform golf ball standards. Fillersmay also be used to modify the weight of the center or at least oneadditional layer for specialty balls, e.g., a lower weight ball ispreferred for a player having a low swing speed.

Materials such as tungsten, zinc oxide, barium sulfate, silica, calciumcarbonate, zinc carbonate, metals, metal oxides and salts, and regrind(recycled core material typically ground to about 30 mesh particle) arealso suitable fillers.

The polybutadiene and/or any other base rubber or elastomer system mayalso be foamed, or filled with hollow microspheres or with expandablemicrospheres which expand at a set temperature during the curing processto any low specific gravity level. Other ingredients such as sulfuraccelerators, e.g., tetramethylthiuram di, tri, or tetrasulfide, and/ormetal-containing organosulfur components may also be used according tothe invention. Suitable metal-containing organosulfur acceleratorsinclude, but are not limited to, cadmium, copper, lead, and telluriumanalogs of diethyldithiocarbamate, diamyldithiocarbamate, anddimethyldithiocarbamate, or mixtures thereof. Other ingredients such asprocessing aids e.g., fatty acids and/or their metal salts, processingoils, dyes and pigments, as well as other additives known to one skilledin the art may also be used in the present invention in amountssufficient to achieve the purpose for which they are typically used.

Without being bound by theory, it is believed that the percentage ofdouble bonds in the trans configuration may be manipulated throughout acore containing at least one main-chain unsaturated rubber (i.e.,polybutadiene), plastic, or elastomer resulting in a trans gradient. Thetrans gradient may be influenced (up or down) by changing the type andamount of cis-to-trans catalyst (or soft-and-fast agent), the type andamount of peroxide, and the type and amount of coagent in theformulation. For example, a formulation containing about 0.25 phr ZnPCTPmay have a trans gradient of about 5% across the core whereas aformulation containing about 2 phr ZnPCTP may have a trans gradient ofabout 10%, or higher. The trans gradient may also be manipulated throughthe cure times and temperatures. It is believed that lower temperaturesand shorter cure times yield lower trans gradients, although acombination of many of these factors may yield gradients of differingand/or opposite directions from that resulting from use of a singlefactor.

In general, higher and/or faster cure rates tend to yield higher levelsof trans content, as do higher concentrations of peroxides,soft-and-fast agents, and, to some extent, ZDA concentration. Even thetype of rubber may have an effect on trans levels, with those catalyzedby rare-earth metals, such as Nd, being able to form higher levels oftrans polybutadiene compared to those rubbers formed from Group VIIImetals, such as Co, Ni, and Li.

The optional intermediate layer(s) are not limited by a particularcomposition for forming the layer(s), and can be formed from anysuitable golf ball composition including, but not limited to, naturalrubber; polybutadiene; polyisoprene; ethylene propylene rubber;ethylene-propylene-diene rubber; styrene-butadiene rubber; butyl rubber;halobutyl rubber; thermoset polyurethane; thermoset polyurea;acrylonitrile butadiene rubber; polychloroprene; alkyl acrylate rubber;chlorinated isoprene rubber; acrylonitrile chlorinated isoprene rubber;polyalkenamer rubber; polyester; polyacrylate; partially- andfully-neutralized ionomer; graft copolymer of ionomer and polyamide;polyester, particularly polyesters modified with a compatibilizing groupsuch as sulfonate or phosphonate, including modified poly(ethyleneterephthalate), modified poly(butylene terephthalate), modifiedpoly(propylene terephthalate), modified poly(trimethyleneterephthalate), modified poly(ethylene naphthenate), including, but notlimited to, those disclosed in U.S. Pat. Nos. 6,353,050, 6,274,298, and6,001,930, the entire disclosures of which are hereby incorporatedherein by reference; polyamides, polyamide-ethers, and polyamide-esters,including, but not limited to, those disclosed in U.S. Pat. Nos.6,187,864, 6,001,930, and 5,981,654, the entire disclosures of which arehereby incorporated herein by reference; polyurethanes, polyureas, andpolyurethane-polyurea hybrids, including, but not limited to, thosedisclosed in U.S. Pat. Nos. 5,334,673, 5,484,870, 6,506,851, 6,756,436,6,835,794, 6,867,279, 6,960,630, and 7,105,623, U.S. Pat. App. Publ. No.2007/0117923, and U.S. Patent Application Serial No. 60/401,047 and Ser.No. 13/613,095, the entire disclosures of which are hereby incorporatedherein by reference; fluoropolymers, including, but not limited to,those disclosed in U.S. Pat. Nos. 5,691,066, 6,747,110 and 7,009,002,the entire disclosures of which are hereby incorporated herein byreference; non-ionomeric acid polymers, i.e., E/X- and E/X/Y-typecopolymers, including, but not limited to, those disclosed in U.S. Pat.No. 6,872,774, the entire disclosure of which is hereby incorporatedherein by reference; metallocene-catalyzed polymers, including, but notlimited to, those disclosed in U.S. Patent Nos. 6,274,669, 5,919,862,5,981,654, and 5,703,166, the entire disclosures of which are herebyincorporated herein by reference; polystyrenes, such aspoly(styrene-co-maleic anhydride), acrylonitrile-butadiene-styrene,poly(styrene sulfonate), polyethylene styrene; polypropylenes,polyethylenes, propylene elastomers, ethylene elastomers, and copolymersof propylene and ethylene; polyvinyl chlorides; polyvinyl acetates,preferably having less than about 9% of vinyl acetate by weight;polycarbonates, blends of polycarbonate/acrylonitrile-butadiene-styrene,blends of polycarbonate/polyurethane, and blends ofpolycarbonate/polyester; polyvinyl alcohols; polyethers, such aspolyarylene ethers, polyphenylene oxides, and block copolymers ofalkenyl aromatics with vinyl aromatics and poly(amic ester)s;polyimides, polyetherketones, and polyamideimides;polycarbonate/polyester copolymers; and combinations of two or morethereof.

Thermoplastic core compositions are optionally treated or admixed with athermoset diene composition to reduce or prevent flow upon overmolding.Optional treatments may also include the addition of peroxide to thematerial prior to molding, or a post-molding treatment with, forexample, a crosslinking solution, electron beam, gamma radiation,isocyanate or amine solution treatment, or the like. Such treatments mayprevent the intermediate layer from melting and flowing or “leaking” outat the mold equator, as thermoset layers are molded thereon at atemperature necessary to crosslink the thermoset layer, which istypically from 280° F. to 360° F. for a period of about 5 to 30 minutes.

The multi-layer core is enclosed with a cover, which may be a single-,dual-, or multi-layer cover, preferably having an overall thicknesswithin a range having a lower limit of 0.010 or 0.020 or 0.025 or 0.030or 0.040 or 0.045 inches and an upper limit of 0.050 or 0.060 or 0.070or 0.075 or 0.080 or 0.090 or 0.100 or 0.150 or 0.200 or 0.300 or 0.500inches. In a particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040 or0.050 inches. In another particular embodiment, the cover consists of aninner cover layer having a thickness of from 0.010 or 0.020 or 0.025inches to 0.035 or 0.050 inches and an outer cover layer having athickness of from 0.010 or 0.020 or 0.025 inches to 0.035 or 0.040inches.

Suitable cover materials include, but are not limited to, polyurethanes,polyureas, and hybrids of polyurethane and polyurea; ionomer resins andblends thereof (e.g., Surlyn® ionomer resins and DuPont® HPF 1000 andHPF 2000, commercially available from E. I. du Pont de Nemours andCompany; lotek® ionomers, commercially available from ExxonMobilChemical Company; Amplify® IO ionomers of ethylene acrylic acidcopolymers, commercially available from The Dow Chemical Company; andClarix® ionomer resins, commercially available from A. Schulman Inc.);polyisoprene; polyoctenamer, such as Vestenamer® polyoctenamer,commercially available from Evonik Industries; polyethylene, including,for example, low density polyethylene, linear low density polyethylene,and high density polyethylene; polypropylene; rubber-toughened olefinpolymers; non-ionomeric acid copolymers, e.g., (meth)acrylic acid, whichdo not become part of an ionomeric copolymer; plastomers; flexomers;styrene/butadiene/styrene block copolymers;styrene/ethylene-butylene/styrene block copolymers; polybutadiene;styrene butadiene rubber; ethylene propylene rubber; ethylene propylenediene rubber; dynamically vulcanized elastomers; ethylene vinylacetates; ethylene(meth)acrylates; polyvinyl chloride resins;polyamides, amide-ester elastomers, and copolymers of ionomer andpolyamide, including, for example, Pebax® thermoplastic polyether andpolyester amides, commercially available from Arkema Inc; crosslinkedtrans-polyisoprene; polyester-based thermoplastic elastomers, such asHytrel® polyester elastomers, commercially available from E. I. du Pontde Nemours and Company, and Riteflex® polyester elastomers, commerciallyavailable from Ticona; polyurethane-based thermoplastic elastomers, suchas Elastollan® polyurethanes, commercially available from BASF;synthetic or natural vulcanized rubber; and combinations thereof.

Compositions comprising an ionomer or a blend of two or more ionomersare particularly suitable cover materials. Preferred ionomeric covercompositions include:

-   -   (a) a composition comprising a “high acid ionomer” (i.e., having        an acid content of greater than 16 wt %), such as Surlyn 8150®;    -   (b) a composition comprising a high acid ionomer and a maleic        anhydride-grafted non-ionomeric polymer (e.g., Fusabond®        functionalized polymers). A particularly preferred blend of high        acid ionomer and maleic anhydride-grafted polymer is a 84 wt        %/16 wt % blend of Surlyn 8150® and Fusabond®. Blends of high        acid ionomers with maleic anhydride-grafted polymers are further        disclosed, for example, in U.S. Pat. Nos. 6,992,135 and        6,677,401, the entire disclosures of which are hereby        incorporated herein by reference;    -   (c) a composition comprising a 50/45/5 blend of Surlyn®        8940/Surlyn® 9650/Nucrel® 960, preferably having a material        hardness of from 80 to 85 Shore C;    -   (d) a composition comprising a 50/25/25 blend of Surlyn®        8940/Surlyn® 9650/Surlyn® 9910, preferably having a material        hardness of about 90 Shore C;    -   (e) a composition comprising a 50/50 blend of Surlyn®        8940/Surlyn® 9650, preferably having a material hardness of        about 86 Shore C;    -   (f) a composition comprising a blend of Surlyn® 7940/Surlyn®        8940, optionally including a melt flow modifier;    -   (g) a composition comprising a blend of a first high acid        ionomer and a second high acid ionomer, wherein the first high        acid ionomer is neutralized with a different cation than the        second high acid ionomer (e.g., 50/50 blend of Surlyn® 8150 and        Surlyn® 9150), optionally including one or more melt flow        modifiers such as an ionomer, ethylene-acid copolymer or ester        terpolymer; and    -   (h) a composition comprising a blend of a first high acid        ionomer and a second high acid ionomer, wherein the first high        acid ionomer is neutralized with a different cation than the        second high acid ionomer, and from 0 to 10 wt % of an        ethylene/acid/ester ionomer wherein the ethylene/acid/ester        ionomer is neutralized with the same cation as either the first        high acid ionomer or the second high acid ionomer or a different        cation than the first and second high acid ionomers (e.g., a        blend of 40-50 wt % Surlyn® 8140, 40-50 wt % Surlyn® 9120, and        0-10 wt % Surlyn® 6320).

Surlyn 8150®, Surlyn® 8940, and Surlyn® 8140 are different grades ofE/MAA copolymer in which the acid groups have been partially neutralizedwith sodium ions. Surlyn® 9650, Surlyn® 9910, Surlyn® 9150, and Surlyn®9120 are different grades of E/MAA copolymer in which the acid groupshave been partially neutralized with zinc ions. Surlyn® 7940 is an E/MAAcopolymer in which the acid groups have been partially neutralized withlithium ions. Surlyn® 6320 is a very low modulus magnesium ionomer witha medium acid content. Nucrel® 960 is an E/MAA copolymer resin nominallymade with 15 wt % methacrylic acid. Surlyn® ionomers, Fusabond®polymers, and Nucrel® copolymers are commercially available from E. I.du Pont de Nemours and Company.

lonomeric cover compositions can be blended with non-ionic thermoplasticresins, particularly to manipulate product properties. Examples ofsuitable non-ionic thermoplastic resins include, but are not limited to,polyurethane, poly-ether-ester, poly-amide-ether, polyether-urea,thermoplastic polyether block amides (e.g., Pebax® block copolymers,commercially available from Arkema Inc.), styrene-butadiene-styreneblock copolymers, styrene(ethylene-butylene)-styrene block copolymers,polyamides, polyesters, polyolefins (e.g., polyethylene, polypropylene,ethylene-propylene copolymers, polyethylene-(meth)acrylate,plyethylene-(meth)acrylic acid, functionalized polymers with maleicanhydride grafting, Fusabond® functionalized polymers commerciallyavailable from E. I. du Pont de Nemours and Company, functionalizedpolymers with epoxidation, elastomers (e.g., ethylene propylene dienemonomer rubber, metallocene-catalyzed polyolefin) and ground powders ofthermoset elastomers.

Ionomer golf ball cover compositions may include a flow modifier, suchas, but not limited to, acid copolymer resins (e.g., Nucrel® acidcopolymer resins, and particularly Nucrel® 960, commercially availablefrom E. I. du Pont de Nemours and Company), performance additives (e.g.,A-C® performance additives, particularly A-C® low molecular weightionomers and copolymers, A-C® oxidized polyethylenes, and A-C® ethylenevinyl acetate waxes, commercially available from Honeywell InternationalInc.), fatty acid amides (e.g., ethylene bis-stearamide and ethylenebis-oleamide), fatty acids and salts thereof

Suitable ionomeric cover materials are further disclosed, for example,in U.S. Pat. Nos. 6,653,382, 6,756,436, 6,894,098, 6,919,393, and6,953,820, the entire disclosures of which are hereby incorporated byreference.

Polyurethanes, polyureas, and blends and hybrids ofpolyurethane/polyurea are also particularly suitable for forming coverlayers. Suitable polyurethanes and polyureas are further disclosed, forexample, in U.S. Pat. Nos. 5,334,673, 5,484,870, 6,506,851, 6,756,436,6,835,794, 6,867,279, 6,960,630, and 7,105,623; U.S. Pat. App. Publ. No.2009/0011868; and U.S. Patent Application Serial No. 60/401,047, theentire disclosures of which are hereby incorporated herein by reference.Suitable polyurethane-urea cover materials include polyurethane/polyureablends and copolymers comprising urethane and urea segments, asdisclosed in U.S. Pat. App. Publ. No. 2007/0117923, the entiredisclosure of which is hereby incorporated herein by reference.

Cover compositions may include one or more filler(s), such as titaniumdioxide, barium sulfate, etc., and/or additive(s), such as coloringagents, fluorescent agents, whitening agents, antioxidants, dispersants,UV absorbers, light stabilizers, plasticizers, surfactants,compatibility agents, foaming agents, reinforcing agents, releaseagents, and the like.

Suitable cover materials and constructions also include, but are notlimited to, those disclosed in U.S. Pat. App. Publ. No. 2005/0164810,U.S. Pat. Nos. 5,919,100, 6,117,025, 6,767,940, and 6,960,630, and PCTPublications WO00/23519 and W000/29129, the entire disclosures of whichare hereby incorporated herein by reference.

In a particular embodiment, the cover is a single layer, preferablyformed from an ionomeric composition having a material hardness of 60Shore D or greater or a material hardness of from 60 or 62 or 65 Shore Dto 65 or 70 or 72 Shore D, and a thickness of 0.02 inches or greater or0.03 inches or greater or 0.04 inches or greater or a thickness within arange having a lower limit of 0.010 or 0.015 or 0.020 inches and anupper limit of 0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches andformed from a thermoplastic composition selected from ionomer-,polyurethane-, and polyurea-based compositions having a materialhardness of 62 Shore D or less, or less than 62 Shore D, or 60 Shore Dor less, or less than 60

Shore D, or 55 Shore D or less, or less than 55 Shore D.

In another particular embodiment, the cover is a single layer having athickness of from 0.010 or 0.025 inches to 0.035 or 0.040 inches andformed from a thermosetting polyurethane- or polyurea-based compositionhaving a material hardness of 62 Shore D or less, or less than 62 ShoreD, or 60 Shore D or less, or less than 60 Shore D, or 55 Shore D orless, or less than 55 Shore D.

In another particular embodiment, the cover comprises an inner coverlayer formed from an ionomeric composition and an outer cover layerformed from a thermosetting polyurethane- or polyurea-based composition.The inner cover layer composition preferably has a material hardness offrom 60 or 62 or 65 Shore D to 65 or 70 or 72 Shore D. The inner coverlayer preferably has a thickness within a range having a lower limit of0.010 or 0.020 or 0.030 inches and an upper limit of 0.035 or 0.040 or0.050 inches. The outer cover layer composition preferably has amaterial hardness of 62 Shore D or less, or less than 62 Shore D, or 60Shore D or less, or less than 60 Shore D, or 55 Shore D or less, or lessthan 55 Shore D. The outer cover layer preferably has a thickness withina range having a lower limit of 0.010 or 0.020 or 0.025 inches and anupper limit of 0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover comprises an inner coverlayer formed from an ionomeric composition and an outer cover layerformed from a thermoplastic composition selected from ionomer-,polyurethane-, and polyurea-based compositions. The inner cover layercomposition preferably has a material hardness of from 60 or 62 or 65Shore D to 65 or 70 or 72 Shore D. The inner cover layer preferably hasa thickness within a range having a lower limit of 0.010 or 0.020 or0.030 inches and an upper limit of 0.035 or 0.040 or 0.050 inches. Theouter cover layer composition preferably has a material hardness of 62Shore D or less, or less than 62 Shore D, or 60 Shore D or less, or lessthan 60 Shore D, or 55 Shore D or less, or less than 55 Shore D. Theouter cover layer preferably has a thickness within a range having alower limit of 0.010 or 0.020 or 0.025 inches and an upper limit of0.035 or 0.040 or 0.050 inches.

In another particular embodiment, the cover is a dual- or multi-layercover including an inner or intermediate cover layer formed from anionomeric composition and an outer cover layer formed from apolyurethane- or polyurea-based composition. The ionomeric layerpreferably has a surface hardness of 70 Shore D or less, or 65 Shore Dor less, or less than 65 Shore D, or a Shore D hardness of from 50 to65, or a Shore D hardness of from 57 to 60, or a Shore D hardness of 58,and a thickness within a range having a lower limit of 0.010 or 0.020 or0.030 inches and an upper limit of 0.045 or 0.080 or 0.120 inches. Theouter cover layer is preferably formed from a castable or reactioninjection moldable polyurethane, polyurea, or copolymer or hybrid ofpolyurethane/polyurea. Such cover material is preferably thermosetting,but may be thermoplastic. The outer cover layer composition preferablyhas a material hardness of 85 Shore C or less, or 45 Shore D or less, or40 Shore D or less, or from 25 Shore D to 40 Shore D, or from 30 Shore Dto 40 Shore D. The outer cover layer preferably has a surface hardnesswithin a range having a lower limit of 20 or 30 or 35 or 40 Shore D andan upper limit of 52 or 58 or 60 or 65 or 70 or 72 or 75 Shore D. Theouter cover layer preferably has a thickness within a range having alower limit of 0.010 or 0.015 or 0.025 inches and an upper limit of0.035 or 0.040 or 0.045 or 0.050 or 0.055 or 0.075 or 0.080 or 0.115inches.

A moisture vapor barrier layer is optionally employed between the coreand the cover. Moisture vapor barrier layers are further disclosed, forexample, in U.S. Pat. Nos. 6,632,147, 6,838,028, 6,932,720, 7,004,854,and 7,182,702, and U.S. Pat. App. Publ. Nos. 2003/0069082, 2003/0069085,2003/0130062, 2004/0147344, 2004/0185963, 2006/0068938, 2006/0128505 and2007/0129172, the entire disclosures of which are hereby incorporatedherein by reference.

Thermoplastic layers herein may be treated in such a manner as to createa positive or negative hardness gradient. In golf ball layers of thepresent invention wherein a thermosetting rubber is used,gradient-producing processes and/or gradient-producing rubberformulation may be employed. Gradient-producing processes andformulations are disclosed more fully, for example, in U.S. patentapplication Ser. Nos. 12/048,665, filed on Mar.14, 2008; Ser. No.11/829,461, filed on Jul. 27, 2007; Ser. No. 11/772,903, filed Jul. 3,2007; Ser. No. 11/832,163, filed Aug. 1, 2007; Ser. No. 11/832,197,filed on Aug. 1, 2007; the entire disclosure of each of these referencesis hereby incorporated herein by reference.

Golf balls of the present invention will typically have dimple coverageof 60% or greater, preferably 65% or greater, and more preferably 75% orgreater.

Additional Construction and Measurement Considerations

The United States Golf Association specifications limit the minimum sizeof a competition golf ball to 1.680 inches. There is no specification asto the maximum diameter, and golf balls of any size can be used forrecreational play. Golf balls of the present invention can have anoverall diameter of any size. The preferred diameter of the present golfballs is within a range having a lower limit of 1.680 inches and anupper limit of 1.740 or 1.760 or 1.780 or 1.800 inches.

Golf balls of the present invention preferably have a moment of inertia(“MOT”) of 70-95 g·cm², preferably 75-93 g·cm², and more preferably76-90 g·cm². For low MOT embodiments, the golf ball preferably has anMOT of 85 g·cm² or less, or 83 g·cm² or less. For high MOT embodiment,the golf ball preferably has an MOT of 86 g·cm² or greater, or 87 g·cm²or greater. MOT is measured on a model MOI-005-104 Moment of InertiaInstrument manufactured by Inertia Dynamics of Collinsville, CT. Theinstrument is connected to a PC for communication via a COMM port and isdriven by MOT Instrument Software version #1.2.

For purposes of the present invention, “compression” refers to Atticompression and is measured according to a known procedure, using anAtti compression test device, wherein a piston is used to compress aball against a spring. The travel of the piston is fixed and thedeflection of the spring is measured. The measurement of the deflectionof the spring does not begin with its contact with the ball; rather,there is an offset of approximately the first 1.25 mm (0.05 inches) ofthe spring's deflection. Very low compression cores will not cause thespring to deflect by more than 1.25 mm and therefore have a zero ornegative compression measurement. The Atti compression tester isdesigned to measure objects having a diameter of 1.680 inches; thus,smaller objects, such as golf ball cores, must be shimmed to a totalheight of 1.680 inches to obtain an accurate reading. Conversion fromAtti compression to Riehle (cores), Riehle (balls), 100 kg deflection,130-10 kg deflection or effective modulus can be carried out accordingto the formulas given in Compression by Any Other Name, Science and GolfIV, Proceedings of the World Scientific Congress of Golf (Eric Thained., Routledge, 2002).

COR, as used herein, is determined according to a known procedurewherein a sphere is fired from an air cannon at two given velocities andcalculated at a velocity of 125 ft/s. Ballistic light screens arelocated between the air cannon and the steel plate at a fixed distanceto measure ball velocity. As the sphere travels toward the steel plate,it activates each light screen, and the time at each light screen ismeasured. This provides an incoming transit time period inverselyproportional to the sphere's incoming velocity. The sphere impacts thesteel plate and rebounds through the light screens, which again measuresthe time period required to transit between the light screens. Thisprovides an outgoing transit time period inversely proportional to thesphere's outgoing velocity. COR is then calculated as the ratio of theoutgoing transit time period to the incoming transit time period,COR=V_(out)/V_(in)=T_(in)/T_(out).

The surface hardness of a golf ball layer is obtained from the averageof a number of measurements taken from opposing hemispheres, taking careto avoid making measurements on the parting line of the core or onsurface defects, such as holes or protrusions. Hardness measurements aremade pursuant to ASTM D-2240 using a calibrated, digital durometer,capable of reading to 0.1 hardness units and set to record the maximumhardness reading obtained for each measurement.

The center hardness of a core is obtained according to the followingprocedure. The core is gently pressed into a hemispherical holder havingan internal diameter approximately slightly smaller than the diameter ofthe core, such that the core is held in place in the hemisphericalportion of the holder while concurrently leaving the geometric centralplane of the core exposed. The core is secured in the holder byfriction, such that it will not move during the cutting and grindingsteps, but the friction is not so excessive that distortion of thenatural shape of the core would result. The core is secured such thatthe parting line of the core is roughly parallel to the top of theholder. The diameter of the core is measured 90 degrees to thisorientation prior to securing. A measurement is also made from thebottom of the holder to the top of the core to provide a reference pointfor future calculations. A rough cut is made slightly above the exposedgeometric center of the core using a band saw or other appropriatecutting tool, making sure that the core does not move in the holderduring this step. The remainder of the core, still in the holder, issecured to the base plate of a surface grinding machine. The exposed‘rough’ surface is ground to a smooth, flat surface, revealing thegeometric center of the core, which can be verified by measuring theheight from the bottom of the holder to the exposed surface of the core,making sure that exactly half of the original height of the core, asmeasured above, has been removed to within ±0.004 inches. Leaving thecore in the holder, the center of the core is found with a center squareand carefully marked and the hardness is measured at the center markaccording to ASTM D-2240. Additional hardness measurements at anydistance from the center of the core can then be made by drawing a lineradially outward from the center mark, and measuring the hardness at anygiven distance along the line, typically in 2 mm increments from thecenter. The hardness at a particular distance from the center should bemeasured along at least two, preferably four, radial arms located 180°apart, or 90° apart, respectively, and then averaged. All hardnessmeasurements performed on a plane passing through the geometric centerare performed while the core is still in the holder and without havingdisturbed its orientation, such that the test surface is constantlyparallel to the bottom of the holder, and thus also parallel to theproperly aligned foot of the durometer.

Hardness points should only be measured once at any particular geometriclocation.

It should be understood that there is a fundamental difference between“material hardness” and “hardness as measured directly on a golf ball.”For purposes of the present disclosure, material hardness is measuredaccording to ASTM D2240 and generally involves measuring the hardness ofa flat “slab” or “button” formed of the material. Hardness as measureddirectly on a golf ball (or other spherical surface) typically resultsin a different hardness value. This difference in hardness values is dueto several factors including, but not limited to, ball construction(i.e., core type, number of core and/or cover layers, etc.), ball (orsphere) diameter, and the material composition of adjacent layers. Itshould also be understood that the two measurement techniques are notlinearly related and, therefore, one hardness value cannot easily becorrelated to the other.

When numerical lower limits and numerical upper limits are set forthherein, it is contemplated that any combination of these values may beused.

All patents, publications, test procedures, and other references citedherein, including priority documents, are fully incorporated byreference to the extent such disclosure is not inconsistent with thisinvention and for all jurisdictions in which such incorporation ispermitted.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by those ofordinary skill in the art without departing from the spirit and scope ofthe invention. Accordingly, it is not intended that the scope of theclaims appended hereto be limited to the examples and descriptions setforth herein, but rather that the claims be construed as encompassingall of the features of patentable novelty which reside in the presentinvention, including all features which would be treated as equivalentsthereof by those of ordinary skill in the art to which the inventionpertains.

What is claimed is:
 1. A golf ball comprising a core and a cover,wherein the core consists of: a solid inner core layer formed from atransparent or plasticized polyamide composition and having a diameterof 1.10 inch or less and a center Shore C hardness (H_(center)) of 50 orless, one or more optional intermediate core layers, and an outer corelayer formed from at least one of a thermoset rubber composition and athermoplastic composition and having a thickness of 0.200 inches orgreater and an outer surface Shore C hardness (H_(outer surface)) of 70or greater, wherein H_(outer surface)>H_(center), andH_(outer surface)−H_(center)≧40.
 2. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧45.
 3. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧50.
 4. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧55.
 5. The golf ball of claim 1, whereinH_(outer surface)−H_(center)≧60.
 6. The golf ball of claim 1, whereinthe inner core layer has an inner core interface Shore C hardnessH_(inner core interface) such that−5≦H_(inner core interface)−H_(center)≦5.
 7. The golf ball of claim 1,wherein the outer core layer has an outer core interface Shore Chardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)≦H_(outer surface)−H_(center).8. The golf ball of claim 1, wherein the outer core layer has an outercore interface Shore C hardness H_(outer core interface) such thatH_(outer core interface)−H_(inner core interface)>H_(outer surface)−H_(center).9. The golf ball of claim 1, wherein the transparent or plasticizedpolyamide composition comprises at least one of a polyether block amide,an amorphous polyamide and a microcrystalline polyamide.
 10. The golfball of claim 1, wherein the outer core layer comprises at least one ofnatural rubber, polybutadiene, polyisoprene, ethylene propylene rubber(EPR), ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber,butyl rubber, halobutyl rubber, polyurethane, polyurea, acrylonitrilebutadiene rubber, polychloroprene, alkyl acrylate rubber, chlorinatedisoprene rubber, acrylonitrile chlorinated isoprene rubber,polyalkenamer, phenol formaldehyde, melamine formaldehyde, polyepoxide,polysiloxane, polyester, alkyd, polyisocyanurate, polycyanurate,polyacrylate, and combinations thereof.
 11. The golf ball of claim 1,wherein the outer core layer comprises at least one of ionomers; highlyneutralized ionomers; non-ionomeric acid polymers; polyurethanes,polyureas, and polyurethane-polyurea hybrids; polyester-basedthermoplastic elastomers; polyamides, copolymers of ionomer andpolyamide, polyamide-ethers, and polyamide-esters; ethylene-basedhomopolymers and copolymers; propylene-based homopolymers andcopolymers; triblock copolymers based on styrene and ethylene/butylene;derivatives thereof that are compatibilized with at least one grafted orcopolymerized functional group; and combinations thereof.
 12. The golfball of claim 1, wherein the intermediate core layer comprises at leastone of ionomers; highly neutralized ionomers; non-ionomeric acidpolymers; polyurethanes, polyureas, and polyurethane-polyurea hybrids;polyester-based thermoplastic elastomers; polyamides, copolymers ofionomer and polyamide, polyamide-ethers, and polyamide-esters;ethylene-based homopolymers and copolymers; propylene-based homopolymersand copolymers; triblock copolymers based on styrene andethylene/butylene; derivatives thereof that are compatibilized with atleast one grafted or copolymerized functional group; and combinationsthereof.
 13. The golf ball of claim 1, comprising an intermediate corelayer formed from at least one of natural rubber, polybutadiene,polyisoprene, ethylene propylene rubber (EPR), ethylene-propylene-dienerubber (EPDM), styrene-butadiene rubber, butyl rubber, halobutyl rubber,polyurethane, polyurea, acrylonitrile butadiene rubber, polychloroprene,alkyl acrylate rubber, chlorinated isoprene rubber, acrylonitrilechlorinated isoprene rubber, polyalkenamer, phenol formaldehyde,melamine formaldehyde, polyepoxide, polysiloxane, polyester, alkyd,polyisocyanurate, polycyanurate, polyacrylate, and combinations thereof.14. The golf ball of claim 1, wherein the solid inner core layer has acenter Shore C hardness (H_(center)) of 40 or less, the outer core layerhas an outer surface Shore C hardness (H_(outer surface)) of 85 orgreater, and wherein H_(outer surface)>H_(center), andH_(outer surface)−H_(center)≧45.
 15. The golf ball of claim 1, furthercomprising an intermediate layer disposed between the outer core layerand the cover.
 16. The golf ball of claim 15, wherein the intermediatelayer comprises at least one of ionomers; highly neutralized ionomers;non-ionomeric acid polymers; polyurethanes, polyureas, andpolyurethane-polyurea hybrids; polyester-based thermoplastic elastomers;polyamides, copolymers of ionomer and polyamide, polyamide-ethers, andpolyamide-esters; ethylene-based homopolymers and copolymers;propylene-based homopolymers and copolymers; triblock copolymers basedon styrene and ethylene/butylene; derivatives thereof that arecompatibilized with at least one grafted or copolymerized functionalgroup; and combinations thereof.